LIBRARY     OF 


i885-IQ56 


MEDICAL    AND    VETERINARY 
ENTOMOLOGY 


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THE  MACMILLAN   COMPANY 

NEW  YORK   •    BOSTON   ■    CHICAGO   •    DALLAS 
ATLANTA   •    SAN    FRANCISCO 

MACMILLAN  &  CO.,  Limited 

LONDON   •    BOMBAY   •    CALCUTTA 
MELBOURNE 

THE  MACMILLAN  CO.  OF  CANADA,  Ltd. 

TORONTO 


MEDICAL  AND  VETERINARY 
ENTOMOLOGY 


A   TEXTBOOK   FOR   USE   IN   SCHOOLS  AND   COLLEGES 
AS  WELL  AS  A  HANDBOOK  FOR  THE  USE  OF 
•  PHYSICIANS,   VETERINARIANS   AND 

PUBLIC    HEALTH   OFFICIALS 


BY 


WILLIAM  B.   HERMS 


ASSOCIATE  PKOFE880K  OF  PARASITOLOGY  IIOTHB  UNIVERSITY  OF  CALIFORNIA,  CONSULTING 

PAEA8ITOLOGI8T   FOR   THE   CALIFORNIA    BTATK   BOARD   OF  HEALTH,    AND 

FSKMERLY   PROFESSOR   OF   ZOOLOGY   AND   PARASITOLOGY    IN 

THE   BAN    FRANCISCO   VETERINARY   COLLEGE 

AUTHOK   OF    "malaria,    CAUSE   AND   CONTROL,"    "A   LABORATORY   GUIDE  TO   THE 

STUDY   OF   PARASITOLOGY,"    "THE    HOUSEFLY   IN   ITS   RELATION   TO   THE 

PUBLIC   HEALTH,"    "  HOUSEFLY  MANAGEMENT,"    ETC. 


Neto  f  0tfe 
THE    MACMILLAN    COMPANY 

1915 

AU  rights  reserved 


Copyright,  1915, 
By  the  MACMILLAN  COMPANY. 

Printed  from  type.     Published  November,  1915. 


Norfaoott  ^reB8 

J.  8.  Gushing  Co.  —  Berwick  &  Smith  Co. 

Norwood,  Mass.,  U.S.A. 


H)eMcate&  to 

MY   STUDENTS   IN  PARASITOLOGY 


PREFACE 

Much  of  the  matter  contained  in  the  following  pages  was  pre- 
pared for  the  press  more  than  six  years  ago,  but  owing  to  the  rapid 
advances  made  in  the  field  of  parasitology,  particularly  concerning 
insects,  the  writer  has  withheld  it  until  this  time,  when,  after  con- 
siderable revision  and  addition,  it  has  seemed  expedient  to  pub- 
lish the  same.  The  manuscript  has  been  in  almost  constant  use  for 
a  period  of  six  years  in  teaching  classes  in  Parasitology,  both  in  the 
University  of  California  and  in  the  San  Francisco  Veterinary  Col- 
lege. It  has  been  the  aim  to  include  herewith  a  large  part  of  the 
writer's  original  work,  some  of  which  has  until  now  remained  un- 
published, as  well  as  the  published  observations  of  many  other 
investigators  in  this  field,  all  of  which  has  gone  to  build  up  the 
foundation  of  the  new  science  of  Medical  Entomology. 

This  book  is  not  intended  to  be  a  comprehensive  treatise,  touch- 
ing all  the  investigations  in  the  field  of  Medical  Entomology,  but 
rather  an  attempt  to  systematize  the  subject  and  to  assist  in  securing 
for  it  a  place  among  the  applied  biological  sciences.  However,  a 
discussion  is  included  of  all  of  the  more  important  diseases  and  irri- 
tations of  man  and  of  the  domesticated  animals  in  which  insects  and 
arachnids  are  concerned,  either  as  carriers  or  as  causative  organisms. 

Owing  to  the  irximense  literature  on  insects  as  relating  to  disease, 
much  of  which  is  widely  scattered,  the  student  in  this  field  must 
spend  considerable  time  in  searching  for  the  desired  information, 
and  what  is  more  important,  the  information  is  not  readily  accessible 
to  the  physician,  the  veterinarian,  the  health  officer  and  the  sani- 
tarian. It  is  therefore  to  be  hoped  that  this  book  will  not  only 
prove  useful  as  a  text,  but  also  as  a  handbook  for  all  individuals 
who  are  professionally  interested  in  the  health  and  well-being  of 
man  and  beast,  as  affected  by  insects  and  arachnids. 

In  the  second  place  detailed  accounts  of  experiments  are  included 
here  and  there,  so  that  the  investigator  might  employ  the  methods 
described  in  either  the  repetition  of  the  work  or  in  carrying  on 
further  investigations  along  the  lines  suggested. 

Although  many  special  papers  have  been  consulted  in  the  prep- 
aration of  this  work,  a  bibliography  is  not  included  herewith,  inas- 
much as  this  information  is  obtainable  in  much  more  complete  form 
in  the  bibliographical  works  of  other  writers.     Reference  to  special 


viii  PREFACE 

papers  is  usually  made  in  footnote  form,  but  where  certain  facts 
have  long  been  accepted  as  common  knowledge,  reference  is  ordi- 
naril}^  omitted. 

Sources  from  which  assistance  has  been  drawn  are  too  numerous 
to  adequately  enumerate,  but  to  all  who  have  contributed  toward 
the  preparation  of  this  work  I  wish  to  express  my  sincere  apprecia- 
tion and  thanks,  but  most  particularly  to  my  advanced  students  in 
parasitology,  who  have  contributed  much  valuable  data,  and  to  ray 
colleagues,  Professor  C.  W.  Woodworth,  Dr.  Edwin  C.  Van  Dyke, 
Dr.  W.  A.  Sawyer,  and  Mr.  S.  B.  Freeborn,  and  to  my  wife,  Lillie 
M.  Herms,  who  have  at  all  times  given  generous  cooperation  and 
kindly  criticism. 

Unless  otherwise  credited  the  illustrations  are  from  photographs 
and  drawings  made  by  the  author  and  various  assistants.  Thanks 
are  due  particularly  to  Dr.  William  Colby  Rucker  for  the  use  of 
flea  drawings,  to  Professor  Herbert  Osborn  for  permission  to  repro- 
duce certain  drawings  of  biting  and  sucking  lice,  to  M.  B.  Mitzmain 
for  photographs  of  Tahanas  striatus,  to  Prof.  J.  S.  Hine  for  photo- 
graphs of  certain  other  Tabanids,  and  to  Mr.  W.  C.  Matthews, 
Scientific  Illustrator,  for  valuable  assistance  in  the  preparation  of 
many  of  the  figures. 

W.  B.  H. 

Berkeley,  California. 


CONTENTS 

CHAPTER   I 

PAGE 

Introduction  1 

Scope  and  methods ;  Economic  considerations ;  Control  of  insect- 
borne  diseases ;  Insect  control ;  Field  observations ;  Popular  opinion. 

CHAPTER  II 

Parasites  and  Parasitism  6 

Parasitism ;  Classes  of  parasites ;  Effect  of  parasitism  on  the  host ; 
Effect  of  parasitism  on  the  parasite;  Origin  of  parasitism;  Systematic 
position  of  animal  parasites. 

CHAPTER   III 

Insect  Anatomy  and  Classification 1^ 

General;  Insect  larvae;  Importance  of  knowing  internal  anatomy; 
Digestive  system ;  Salivary  system  ;  Wings  ;  Metamorphosis ;  External 
Anatomy ;  Key  to  classification. 

CHAPTER   TV 

Insect  Mouth  Parts .      -3 

Importance  of  mouth  parts;  Classification  of  mouth  parts;  The  Or- 
thopteron  type;  Physopodan  type;  Hemipteron  type;  Dipteron  type; 
Hymenopteron  type  ;  Lepidopteron  type. 

CHAPTER  V 

How  Insects  Carry  and  Cause  Disease 33 

Environmental  considerations;  How  insects  carry  disease;  How  in- 
sects cause  disease ;  Direct  infection ;  Indirect  infection ;  Internal 
parasitism  ;  External  parasitism  ;  Insect  venoms. 

CHAPTER   VI 

Cockroaches,  Beetles,  Thrips  37 

The  cockroaches ;  Habits  ;  Life  History ;  Species  and  distribution  ; 
The  croton  bug;  Relation  to  disease  transmission;  Environmental  con- 
siderations; Control;  The  Beetles;  Scavenger  beetles;  Relation  to 
disease ;  May  beetles  and  thorn-headed  worms ;  Saw-toothed  grain 
beetles;  Cantharidin,  — Spanish  fly  ;  The  Thrips;    Thrips  and  sneezing. 


CONTENTS 


CHAPTER   VII 

PAOS 

The  Lice 52 

The  biting  lice;  Habits  and  life  history;  Damage, done;  Species  of 
Trichodectidse ;  Species  of  Philopteridae;  Gyropidae;  Liotheidse ;  To 
control  poultry  lice;  The  sucking  lice;  Life  history;  Pediculosis; 
Species  affecting  man ;  Species  affecting  domesticated  animals ;  Relation 
to  disease ;  Impetigo ;  Spirochaetosis ;  Typhus  fever ;  Relation  to  Ento- 
parasites;  Treatment  and  control ;  Control  on  animals. 

CHAPTER   VIII 

Bedbugs  and  Cone-noses 69 

The  bedbugs;  Characterization;  The  common  bedbug;  Habits  and 
life  history;  Method  of  distribution;  Relation  to  disease;  Anthrax; 
Kala-azar;  Spirochaetosis;  Control;  Fumigation;  The  Cone-noses  ;  Spe- 
cies descriptions ;  Life  history ;  Relation  to  disease  ;  Chagas  disease ; 
Control ;  Treatment  for  bite. 

CHAPTER   IX 

Mosquitoes 80 

General  characteristics;  Nearest  allies;  Life  history;  Internal  anat- 
omy ;  Characters  of  systematic  value  ;  Anopheline  mosquitoes ;  Life 
history;  Duration  of  adult  life  ;  Flight;  Hibernation;  Breeding  places  ; 
Yellow  fever  mosquitoes;  Life  history;  Classification  of  mosquitoes; 
Key  to  common  species. 

CHAPTER  X 

Mosquitoes  as  Disease  Beakers 101 

Malaria;  Mosquito  transmission;  Circumstantial  evidence;  Experr- 
mental  evidence;  Description  and  life  history  of  Plasmodia;  Yellow 
fever ;  Stegomyia  the  carrier ;  Time  factor ;  Filariasis  ;  Dengue ;  Ver- 
ruga ;  Phlebotomus  flies. 

CHAPTER   XI 
Mosquito  Control 120 

Where  mosquitoes  breed;  Essentials  of  control;  Oiling  methods; 
Tobacco  decoctious  ;  Other  larvaecides ;  Permanent  corrections;  Irriga- 
tion; River  towns  and  malaria;  Salt  marsh  mosquitoes;  Summer  re- 
sorts; Screening;  Repellents;  Natural  enemies;  Organization  of 
campaigns;  Cost;  When  to  begin  work  and  when  to  close;  Educational 
factor;  Legislation;  Economic  considerations;  Malaria  reduction ;  Yel- 
low fever  reduction. 

CHAPTER   XII 

Buffalo  Gnats  and  Horseflies 143 

Buffalo  gnats  ;  Breeding  habits  and  life  history  ;  The  bite  ;  Relation 
to  disease  ;  Pellagra ;  Control ;  Systematic  ;  Horseflies  ;  Breeding  habits 
and  life  history;  Bites;  Relation  to  anthrax;  Relation  to  surra;  Con- 
trol; Svstematic. 


CONTENTS  xi 


CHAPTER   XIII 

PAGE 

The  Common  House  Fly 160 

Characteristics  of  the  house  fly  ;  Life  history ;  lufluence  of  tempera- 
ture on  life  history;  Breeding  places;  Range  of  flight;  Longevity; 
Relation  to  light;"  Relation  to  disease;  Evidence;  Typhoid  fever; 
Dysentery;  Summer  Diarrhea;  Tuberculosis;  Asiatic  cholera;  Yaws; 
Ophthalmia;  Eggs  of  parasitic  worms. 


CHAPTER   XIV 

House  Fly  Control 184 

Introduction;  Sanitary  stable  construction;  Disposal  of  manures; 
Manure  bins;  Garbage  cans;  The  sanitary  privy;  Insecticides  on 
manure ;  Hot  water  method ;  The  fly  in  the  house ;  Fly  poisons ;  Natural 
enemies;  The  community  fly  crusade  ;  Manure,  stable  and  fly  ordinances. 


CHAPTER   XV 

Blood-sucking  Muscids,  —  Tsetse  Flies,  Stable  Flies,  Horn  Flies  .     207 

The  tsetse  flies;  Habits;  Structural  characteristics;  Life  history; 
Trypanosomiasis ;  Sleeping  sickness ;  Nagana ;  Control ;  Species  of 
Glossina  flies;  Stomoxys  or  Stable  flies;  Habits;  Light  reactions; 
Breeding  habits  and  life  history;  Longevity;  Surra;  Poliomyelitis; 
Control;  Systematic;  The  horn  fly;  Life  history;  Damage  done; 
Control. 


CHAPTER   XVI 

Myiasis 233 

Myiasis;  Dipterous  larvae;  Flesh  flies;  Texas  screw  worm  fly;  As 
affecting  man;  As  affecting  domesticated  animals;  Other  flesh  flies; 
The  Congo  flour  maggot;  Treatment  for  nasal  myiasis;  Treatment  for 
animals ;  Preventive  measures ;  Anthomyiid  flies ;  Gastric  and  intestinal 
myiasis ;  Rat-tailed  larvae ;  Botflies ;  Horse  bots ;  Treatment  for  bots  ; 
Preventive  measures;  Ox  warbles;  Injury  done;  Economic  losses; 
Treatment  for  warbles;  Prevention;  Head  maggot  of  sheep;  Treat- 
ment; Prevention;  Bots  in  rodents;  Warbles  in  humans;  Key  to  the 
determination  of  species  of  fly  larvse  involved  in  myiasis. 


CHAPTER  XVII 

Fleas  and  Louse  Flies 266 

Fleas,  Characteristics ;  Life  history ;  Longevity  of  fleas  ;  Hosts  and 
occurrence  of  species;  Systematic;  The  commoner  species;  Plague; 
Plague  transmission;  How  the  flea  receives  and  transmits  plague; 
Squirrels  and  plague;  Flea  control;  Treatment  of  doniesticated  animals 
for  fleas ;  Rat  control ;  Squirrel  control  ;  The  Chigoe  flea  ;  Patho- 
genesis; Treatment  and  control;  The  hen  flea;  To  control  the  hen  flea; 
Louse  flies  and  forest  flies ;  Life  history  ;  Pathogenesis  ;  Control ;  Louse 
fly  of  the  deer. 


xii  CONTENTS 

CHAPTER   XVIII 

PAGE 

Ticks "■^96 

Characteristics  of  Arachnida;  Characteristics  of  the  Ixodoidea 
(Ticks);  Life  history;  Tick  mouth  parts ;  Feeding  habits ;  Longevity; 
Texas  cattle  fever  tick :  Economic  importance ;  Life  history  of  Texas 
fever  tick;  Texas  fever  (PiroiMasmosis)  ;  Control  of  Texas  fever; 
African  coast  fever;  Rocky  Mountain  spotted  fever;  Other  piroplas- 
moses;  Other  common  Ixodine  Ticks;  The  Argasine  Ticks;  African 
Relapsing  Fever  Tick;  Spirochsetosis;  Spinose  Ear  Tick;  The  Paja- 
roello;  The  Poultry  Tick. 

CHAPTER   XIX 

Mites 330 

Mite  characteristics ;  Acariasis ;  Sarcoptic  acariasis ;  Mange  and 
Itch;  Remedies  for  Mange  and  Itch;  Psoroptic  acariasis;  Sheep  scab; 
Life  history  of  scab  mite;  Control  of  scabies;  Scaly  leg  of  poultry; 
The  follicle  mites ;  Harvest  mites ;  Louse-like  mites ;  Poultry  mites. 

CHAPTER   XX 

Venomous       Insects     and     Arachnids,  —  Bees,      Wasps,      Spiders, 

Scorpions,  etc. 351 

Insect  venoms  ;  How  introduced;  The  Insect  sting;  Bees  and  wasps  ; 
Spiders;      The    poisonous    Latrodectes;     Tarantulas;    Scorpions;     The 
Pajaroello  ;  Other  ticks ;  Cone-noses  ;  The  Vinegerone. 


APPENDIX   I 
General  Classification  of  Bacteria  and  Protozoa     ....     375 


MEDICAL  AND  VETERINARY 
ENTOMOLOGY 


CHAPTER   I 
INTRODUCTION 

Scope  and  Methods.  —  Medical  Entomology  is  concerned  with  the 
study  of  insects  and  arachnids  as  they  relate  to  the  transmission  and 
causation  of  disease  in  man  and  beast,  and  is,  therefore,  a  specialized 
branch  of  the  science  of  Parasitology.  Mosquitoes  and  flies  have  for 
centuries  past  been  looked  upon  as  a  source  of  extreme  annoyance  to 
the  human  family,  and  students  of  animal  husbandry  and  of  veterinary 
medicine  early  recognized  the  importance  of  lice,  flies  and  ticks  as 
sources  of  irritation  to  horses,  cattle,  hogs,  etc.  But  that  insects  and 
arachnids  could  be  transmitters  of  disease  was  not  considered  seriously 
until  the  latter  part  of  the  last  century,  and  that  certain  species  could 
be  the  sole  transmitters  of  specific  diseases  was  scarcely  suspected  until 
the  latter  few  years  of  the  past  and  the  beginning  of  this,  the  twentieth, 
century.  To-day  our  knowledge  of  disease  transmission  by  insects 
has  been  greatly  augmented  by  the  w^ork  of  a  host  of  individual  investi- 
gators representing  various  departments  of  scientific  research,  such  as 
Medicine,  Veterinary  Medicine,  Bacteriology,  Hygiene,  Zoology  and 
Entomology. 

The  usual  training  received  in  any  one  of  the  departments  above 
mentioned  is  necessarily  of  such  a  nature  as  to  handicap  any  one  under- 
taking health  problems  in  which  insects  and  arachnids  are  concerned. 
Therefore,  to  meet  the  ever  growing  demand  for  investigators  in  this 
rich  field,  and  to  satisfy  the  question  of  responsibility,  the  science  of 
Medical  Entomology  has  been  evolved.  This  science  shares  a  portion 
of  the  fields  of  Pathology,  Bacteriology  and  Entomology ;  the  first,  in 
that  certain  phases  of  pathology  are  involved ;  the  second,  in  that 
pathogenic  bacteria  and  protozoa  are  concerned ;  and  the  third,  in  that 
the  systematic  and  biological  relationships  of  the  insect  must  be  studied 
as  well  as  the  morphology  of  its  mouth  parts  and  digestive  system.  For 
example,  in  the  study  of  malaria,  blood  corpuscles  are  involved,  calling 
for  a  knowledge  of  both  normal  and  diseased  human  blood  ;  an  intimate 
knowledge    of    blood    parasites    is    imperative;    and    the    insect  host, 

1 


2  MEDICAL    AND   VETERINARY  ENTOMOLOGY 

the  Anopheles  mosquito,  must  receive  particular  attention,  as  to  its 
identification,  anatomy  and  habits.  It  is  evident  at  once  that  a  knowl- 
edge of  the  details  of  these  three  phases  requires  a  specific  training. 

The  ultimate  aim  of  the  science  of  Medical  Entomology  is  the  pre- 
vention of  diseases  in  which  insects  are  concerned ;  it  is  therefore  an 
important  adjunct  to  Preventive  Medicine  and  Public  Health. 

Notable  instances  where  the  control  of  certain  diseases  has  depended 
upon  the  control  of  insects  are,  as  is  well  known,  the  mosquito  campaigns 
of  Cuba,  Panama  Canal  Zone  and  the  southern  United  States  to  control 
yellow  fever  mainly,  and  in  New  Jersey,  California,  Italy  and  portions  of 
Africa  to  control  malaria.  Lately  much  attention  has  been  paid  the 
common  house  fly  ;  inasmuch  as  it  has  proved  a  gross  carrier  of  certain 
enteric  or  intestinal  diseases,  campaigns  of  considerable  proportions 
have  been  waged  against  this  insect  in  many  American  cities  from  the 
Atlantic  to  the  Pacific.  One  of  the  most  notable  examples  of  preventive 
work  is  that  accomplished  in  San  Francisco  in  the  control  of  rats  and 
rat  fleas,  thereby  exterminating  bubonic  plague  in  that  city  and  pre- 
venting its  spread. 

The  very  close  bond  between  Preventive  Medicine  and  our  present 
subject  is  at  once  evident,  and  its  significance  becomes  more  and  more 
apparent  as  men  devote  themselves  to  this  highly  fertile  field  of  investi- 
gation. 

Economic  Considerations.  —  In  this  age  of  universal  progress, 
efficiency  has  been  made  the  keynote,  and  losses  traceable  to  disease  are 
now  estimated  very  closely  on  a  money  basis.  Even  human  life  is  given 
a  definite  monetary  valuation.  Thus  the  California  State  Board  of 
Health  has  estimated  that  malaria  costs  the  state  of  California  .$2,820,400 
annually,  and  this  state  is  largely  free  from  that  disease.  An  attempt 
to  estimate  the  loss  due  to  malaria  in  any  one  of  the  intensely  malarial 
states  of  the  South,  would  produce  staggering  results. 

The  above  sum  is  based  on  the  following  items,  viz.,  death  of  112 
citizens,  average  value  S1700  ;  6000  acute  cases  of  malaria  at  an  average 
of  $20  per  year  for  drugs,  etc. ;  6000  citizens'  earning  power  reduced 
25  per  cent  by  malaria  (estimated  average  income  $800) ;  loss  of  life, 
wages  and  illness  from  other  diseases  given  opportunity  through  lowered 
resistance  brought  about  by  malaria,  estimating  50  deaths  at  $1700,  and 
1000  persons  ill  at  $100  each ;  loss  through  sacrifice  sales  of  farms  and 
moving  expenses  of  families  leaving  malarial  districts,  estimating  250 
families  at  $500 ;  loss  through  depreciation  in  land  values,  estimating 
$1  per  acre  only  on  1,000,000  acres  under  irrigation  in  parts  concerned. 
Nearly  or  quite  all  of  this  loss  could  be  prevented  by  mosquito  control 
efforts. 

Reduction  in  value  of  real  estate  in  mosquito-infested  regions  is  quite 
unnecessary.  Otherwise  very  desirable  agricultural  land  is  often,  made 
unproductive  because  of  hordes  of  mosquitoes  attacking  man  and  beast ; 
and  again  otherwise  desirable  locations  for  summer  homes  are  made 


INTRODUCTION  3 

uninhabitable  because  of  the  mosquito  nuisance,  —  all  of  which  could 
be  remedied  at  a  comparatively  small  cost.  Real  estate  dealers  have 
hardly  begun  to  avail  themselves  of  the  services  rendered  by  the  study  of 
these  conditions. 

The  expense  incurred  in  the  United  States  in  the  purchase  of  fly 
traps,  sticky  fly  paper,  fly  poison,  etc.,  must  certainly  exceed  two  millions 
of  dollars  annually,  and  Howard,^  in  a  timely  work  on  the  economic  loss 
due  to  insects  that  carry  disease,  estimates  the  cost  of  screening  at  over 
ten  millions  of  dollars  per  annum. 

As  affecting  the  animal  industry  equally  large  losses  are  involved. 
According  to  the  year  book  of  the  United  States  Department  of  Agri- 
culture for  1904,  the  losses  occasioned  by  Texas  fever,  solely  transmitted 
by  a  tick  (Margaropus  annulatus),  amounted  to  about  $100,000,000. 
Ransome,  in  Tanners'  Work  for  October,  1913,  estimates  the  total  loss 
produced  by  the  '  ox  warble  fly '  {Hyyoderma  lineata),Sit  from  S55,000,000 
to  §120,000,000  per  year  for  the  United  States  alone. 

No  effort  has  been  made  to  estimate  the  losses  caused  by  the  Texas 
screw  worm  and  the  horn  fly  as  affecting  cattle,  the  former  producing  a 
direct  loss,  while  the  latter  produces  largely  an  indirect  loss  due  to  irri- 
tation, involving  loss  of  flesh,  poor  growth,  reduction  in  milk  secretion,  etc. 

To  poultry  raisers  the  losses  due  to  the  fowl  tick  {Argas  persicns)  and 
the  poultry  mite  {Dermanyssus  gallince)  must  also  be  quite  considerable. 

Control  of  Insect-borne  Diseases. — Manifestly  the  control  of  insect- 
borne  diseases  depends  on  two  general  conditions.  The  first  is  the 
control  of  the  focus,  through  which  the  insect  becomes  infected,  the 
insect  being  commonly  only  a  carrier,  and  not  a  permanent  receptacle. 
In  the  case  of  certain  infectious  diseases  in  which  the  germ  is  found  in  the 
dejecta,  i.e.  feces  and  sputum,  proper  sanitary  precautions  are  impera- 
tive ;  thus  properly  constructed  fly-tight  privies  prevent  in  large  measure 
the  transmission  of  typhoid  and  dysentery  by  flies ;  the  use  of  paper 
sputum  cups  (cups  to  be  burned)  and  fly-tight  cuspidors  by  victims  of 
tuberculosis  prevents  in  large  measure  the  spread  of  this  disease  by  flies. 
The  rigid  enforcement  of  "  anti-spitting  "  laws  and  ordinances  regulating 
the  construction  of  privies  will  bring  about  good  results.  Again,  proper 
regulations  requiring  patients  known  to  be  ill  with  insect-borne  diseases 
to  be  screened  against  insects,  prevent  wholesale  infection.  Thus 
yellow  fever  quarantine  is  imperative  in  order  to  prevent  the  mosquito 
carrier  (Aedes  calopus)  from  becoming  infected.  If  such  regulations 
were  applied  to  malaria,  there  would  be  much  less  of  this  disease.  How- 
ever, in  this  latter  case,  quarantine  would  cause  much  hardship,  because 
the  patient  may  not  be  ill  enough  to  require  close  confinement,  and  yet 
there  is  every  opportunity  to  infect  the  Anopheline  carrier.  A  further 
element  of  importance  enters  in,  namely  immunity,  under  which  condi- 

'  Howard,  L.  O.,  1909.  Economic  loss  to  the  people  of  the  United  States 
through  insects  that  carry  disease.  U.  S.  Dept.  of  Agr.,  Bureau  of  Entomology, 
Bull.  No.  78. 


4  MEDICAL  AND   VETERINARY  ENTOMOLOGY 

tion  the  infected  carrier  is  not  a  menace,  as  in  the  case  of  yellow 
fever. 

The  second  factor  in  the  control  of  insect-borne  diseases  is  the 
practical  extermination  or  control  of  the  carrier,  i.e.  the  insect.  This 
is  the  safest  and  surest  method. 

Insect  Control.  —  In  the  control  of  disease-transmitting  insects,  the 
most  vulnerable  point  in  the  life  history  is  sought,  and  the  most  effec- 
tive combative  methods  are  then  applied.  This  involves  an  intimate 
knowledge  of  life  history  and  habits.  The  more  familiar  we  are  with 
regard  to  these  two  factors,  the  better  equipped  are  we  to  cope  with  the 
problems  of  control. 

The  application  of  control  measures  may  be  either  of  a  temporary 
or  permanent  nature.  Temporary  control  involves  the  elimination  of 
a  nuisance  for  a  short  time,  a  few  hours  or  a  few  days,  requiring  constant 
repetition ;  for  example,  the  use  of  formaldehyde  to  kill  flies,  or  penny- 
royal or  citronella  to  repel  mosquitoes,  or  even  oil  as  applied  to  mosquito- 
breeding  pools.  Permanent  control,  on  the  other  hand,  involves  the 
elimination  of  breeding  places,  or  permanent  protection  of  the  same  by 
mechanical  or  chemical  means,  to  prevent  the  deposition  of  insect  eggs, 
for  example,  draining  or  filling  up  unnecessary  ponds  and  pools  of  stand- 
ing water,  in  which  mosquitoes  may  breed ;  or  placing  horse  manure 
and  general  refuse  in  receptacles  made  fly-tight  in  order  to  forestall  the 
breeding  of  house  flies. 

Permanent  control  measures,  when  feasible,  will  always  be  far  less 
expensiAe  in  the  end,  and  also  very  much  more  effective  than  the  use  of 
temporary  agents  in  the  form  of  insecticides,  which  must  be  applied 
over  and  over  again,  with  continuous  expenditure  of  time,  labor  and 
money.  Standing  water  can  often  be  drained  off  with  little  expense, 
whereas  the  repeated  application  of  oil  must  eventually  involve  greater 
outlay  and  inconvenience.  To  illustrate,  the  writer  at  one  time  observed 
a  small  pond  which  was  surely  furnishing  most  of  the  mosquitoes  for  the 
neighborhood ;  it  was  the  only  pond  near,  and  was  within  ten  feet  of 
a  rapidly  running  stream  lower  in  elevation  than  the  pond  by  at  least 
eighteen  inches.  This  pond  could  have  been  drained  very  easily  and 
would  have  resulted  in  permanent  prevention  ;  however,  oil  was  being 
applied  regularly.  The  pool  was  evidently  of  no  use  to  any  one,  and 
was  within  the  limits  of  a  mosquito  campaign.  Again,  the  common 
house  fly,  a  source  of  so  much  annoyance,  is  ordinarily  combated  with 
poisons,  sticky  fly  paper  and  screens,  when  the  mere  removal  of  perhaps 
a  single  horse  manure  pile  in  the  immediate  vicinity  would  speedily 
give  ready  and  permanent  relief. 

Field  Observations.  —  In  the  practical  control  of  insects  the  obser- 
vations made  in  the  field  are  indispensable  to  the  correct  interpretation 
of  laboratory  or  clinical  observations.  A  parasite  removed  from  its 
normal  host  and  brought  under  unnatural  conditions  may  not  function 
normally,  the  reproductive  function  is  commonly  disturbed,  few  or  no 


INTRODUCTION  5 

eggs  being  deposited  in  captivity,  or  if  so,  they  may  not  be  fertile. 
Therefore,  it  is  far  preferable  to  carry  on  observations  where  life  history 
is  concerned  in  the  field  or  under  fairly  natural  conditions. 

Popular  Opinion.  —  A  crusade  against  disease-transmitting  organ- 
isms such  as  insects  always  brings  with  it  a  storm  of  opposition  on  the 
part  of  not  a  few  people,  who  contend  that  it  is  a  breach  of  trust  with 
Nature  to  proceed  against  any  species  already  in  existence.  Few  ideas 
are  more  firmly  rooted  in  the  mind  of  the  average  man  or  woman  than 
that  Nature  has  brought  forth  nothing  that  is  useless  in  the  economy 
of  the  human  family.  It  must  be  good  for  something,  otherwise  it 
would  not  be  in  existence,  and  should,  therefore,  not  be  exterminated  or 
even  molested.  True  it  is,  that  we  must  study  Nature's  ways  and 
endeavor  to  find  out  what  she  is  trying  to  do,  then  help  her  carry  out 
her  plans  more  quickly  and  more  accurately.  For  instance,  if  Nature  has 
provided  scavengers,  she  is  endeavoring  to  clean  up,  thus  pointing  out 
to  man  what  he  should  do.  The  house  fly  is  often  spoken  of  as  one  of 
Nature's  scavengers.  By  a  careful  study  of  the  performance  of  this 
function  by  the  fly,  it  can  be  determined  without  question  that  this 
insect  is  a  very  poor  scavenger,  and  that  this  function  is  carried  on  better 
by  other  insects  {e.g.  certain  flesh  flies)  which  do  not  commonly  relate 
to  human  food  as  does  the  house  fly,  if  indeed  this  argument  should 
be  necessary.  Certainly  no  one  would  contend  that  it  is  necessary  to 
be  infested  with  vermin  as  a  substitute  for  bodily  cleanliness,  and  surely 
no  one  would  argue  that  it  is  a  breach  of  trust  with  Nature  to  annihilate 
the  Anopheles  and  Stegomyia  mosquitoes,  the  transmitters  of  malaria 
and  yellow  fever  respectively. 


CHAPTER  II 
PARASITES  AND  PARASITISM 

Parasitism.  —  It  is  well  that  a  distinction  be  made  at  this  time 
between  parasitic  and  predaceous  insects,  though  the  two  groups  will 
not  remain  distinct  throughout  all  species,  since  the  beginnings  of  para- 
sitism may  not  be  readily  distinguishable  from  the  predaceous  habit. 
It  is  evident  that  a  parasite  can  only  be  a  parasite  as  it  lives  directly  at 
the  expense  of  another  organism,  whether  plant  or  animal.  This  defi- 
nition, however,  leaves  few  animals,  if  any,  out  of  the  category,  inas- 
much as  the  dependence  of  animals  directly  on  other  animals  or 
plants  for  food  is  obvious.  But  if  we  restrict  this  meaning  to  position, 
living  in  or  ujjon  another  animal  or  plant  for  purposes  of  food,  we  come 
nearer  to  the  thought.  But  even  here  there  are  many  organisms  which 
live  in  or  upon  living  animals  or  plants,  but  merely  share  their  food 
with  them  without  causing  injury,  —  this  we  would  term  commensal- 
ism.  Furthermore,  organisms  feeding  in  or  upon  dead  bodies  would 
not  be  termed  parasites,  except  as  they  also  attack  or  feed  on  living 
tissue,  as  in  the  case  of  certain  flesh  flies,  e.g.  the  Texas  screw  worm, 
fly  {Chrysomyia  macellaria  Fabr.),  which  as  a  larva  may  feed  on  the 
flesh  of  either  dead  or  living  animals.  Parasitism,  then,  involves  the 
process  of  one  organism  (the  parasite)  feeding  upon  another  living 
organism  (the  host),  which  host  must  not  be  destroyed  before  at  least 
the  developmental  or  larval  period  of  the  parasite  is  completed,  other- 
wise the  result  would  be  disastrous  to  the  parasite  as  well  as  to  the  host. 

The  definition  given  by  Braun  Ms  "  By  the  term  Parasites  is  understood 
living  organisms,  which  for  the  purpose  of  procuring  food,  take  up  their 
abode,  temporarily  or  permanently,  on  or  within  other  living  organ- 
isms." This  definition  will  exclude  predaceous  animals  (Raubtiere), 
which  capture  their  prey  alive  and  usually  kill  it  outright  for  purposes 
of  food. 

Classes  of  Parasites.  —  Other  than  the  two  general  classes.  Ecto- 
parasites (external  parasites)  and  Entoparasites  (internal  parasites), 
all  parasites  may  be  placed  in  one  of  the  following  divisions,  according 
to  the  time  spent  on  or  within  the  host.  Facultative  parasites  have  the 
power  of  changing  from  one  host  to  another  of  a  different  species,  e.g. 
the  cat  and  dog  flea  {Ctenocephalus  canis  Curtis)  which  may  be  found 

1  Braun,  Max,  1905.  The  Animal  Parasites  of  Man.  William  Wood  and 
Company,  New  York,     xviii  +  4.53  pp. 

6 


PARASITES  AND   PARASITISM  7 

on  the  cat,  the  dog,  the  rat  and  man ;  the  rat  flea  (Ceratophyllus  fas- 
ciatus  Bosc.)  on  the  rat  and  man ;  the  wood  tick  {Dermacentor  varia- 
bilis Say)  may  be  found  on  nearly  all  species  of  domesticated  mammals 
and  man.  Obligatory  parasites  are  restricted  to  one  species  of  host, 
on  which  they  are  obliged  to  remain  throughout  their  life  history, 
e.g.  the  biting  bird  lice  (Mallophaga),  which  perish  if  removed  from  the 
host  or  if  transferred  to  another  species  of  animal.  Intermittent  para- 
sites prey  on  the  host  at  intervals,  coming  only  to  feed,  after  which 
they  leave  again,  e.g.  female  horseflies  (Tabanidse)  in  their  relation  to 
horses  and  cattle  ;  or  the  bedbug  {Cimex  lectularius  Linn.)  in  its  relation 
to  man.  Transitory  parasites  pass  only  part  of  their  life  history  at  the 
expense  of  a  given  host  and  are,  during  that  time,  obligatory,  e.g.  the 
horse  botflies  {Gastrophilus  equi  Fabr.),  which  pass  their  larval  or 
developmental  period  within  the  stomach  of  the  host,  the  adults  being 
free-living ;  or  in  other  transitory  parasites  the  remaining  portion  of 
the  life  history  may  be  spent  at  the  expense  of  an  entirely  difterent 
species  of  host,  as  is  the  case  in  tapeworms. 

Effect  of  Parasitism  on  the  Host.  —  That  an  animal  is  parasitized 
does  not  necessarily  involve  it  in  death,  nor  even  in  great  inconvenience, 
even  though  the  parasite  is  actually  living  at  its  expense.  The  presence 
of  a  few  bots  in  the  stomach  of  a  horse  may  not  affect  that  animal  in 
the  least,  nor  would  the  presence  of  a  few  lice  on  the  body  of  an  ox. 
But  with  the  multiplication  of  these  parasites  there  will  be  increased 
inconvenience  to  both  hosts.  The  presence  of  a  few  maggots  in  the  fleshy 
part  of  a  sheep's  tail  might  cause  little  damage,  but  let  these  be  in  the 
nasal  sinuses  or  in  the  brain,  then  the  gravity  of  the  situation  becomes 
greatly  augmented.  Thus  the  effect  of  parasitism  on  the  host  is  de- 
pendent both  on  the  number  and  position  of  the  parasite. 

Effect  of  Parasitism  on  the  Parasite.  —  All  parasites  are  more  or  less 
specialized  in  the  direction  of  their  habits ;  e.g.  fleas  are  laterally  com- 
pressed, to  effect  ease  of  motion  between  hairs ;  lice  are  horizontally 
flattened,  and  are  provided  with  strong  clasping  organs  by  means  of 
which  they  hold  fast  to  hairs ;  both  of  these  examples  are  wingless  and 
have  sacrificed  much  of  the  ordinary  means  of  locomotion.  Ento- 
parasites  are  usually  provided  with  specialized  hooks,  barbs,  suckers, 
etc.,  for  purposes  of  attachment  to  the  alimentary  canal  or  other  organs, 
e.g.  the  botfly  larvae,  and  among  the  Helminthes,  the  flukes  (Trematoda), 
the  tapeworms  (Cestoda),  etc.  Perhaps,  because  of  the  ease  with 
which  food  is  secured,  the  sense  organs  are  usually  not  strongly  devel- 
oped ;  the  eyes  may  be  very  simple  or  wanting.  The  mouth  parts  differ 
in  the  several  groups,  depending  on  the  special  habits  of  the  insect.  It 
is  interesting  to  note  that  the  parasitic  habit  has  resulted  in  the  devel- 
opment of  structural  similarity.  This  is  particularly  apparent  in  the 
clasping  structures  of  the  biting  and  sucking  lice,  which  belong  system- 
atically to  two  different  orders;  namely,  the  Mallophaga  and  the 
Hemiptera,  respectively. 


8  MEDICAL  AND   VETERINARY  ENTOMOLOGY 

Origin  of  Parasitism.  —  Modern  parasites  are  restricted  more  or 
less  completely  to  particular  host  animals,  which  necessitates  the  deduc- 
tion that  the  parasite  must  have  developed  its  habit  after  the  existence 
of  the  host,  and  in  consequence  parasitism  must  be  a  recently  acquired 
habit  on  the  part  of  a  one-time  free-living  organism.  This  becomes  more 
apparent  by  a  study  of  the  life  history  of  the  parasite ;  invariably  the 
earlier  stages  point  to  a  primitively  free-living  existence.  Perhaps  the 
ancestors  of  a  given  group  of  modern  parasites  were  attracted  to  the  waste 
food,  offal  and  exudations  of  certain  animals ;  the  search  for  food  having 
become  simplified,  they  began  living  as  messmates,  or  commensalists,  or 
as  scavengers ;  the  association  between  the  two  species  became  closer  and 
eventually  the  line  of  parasitism  was  completed.  This  is  also  borne 
out  by  a  study  of  the  nearest  allies  of  a  given  parasite,  in  which  the 
gradation  from  the  free-living  animal  to  the  parasite  may  be  traced. 
The  very  close  structural  similarity  between  the  free-living,  wingless 
book  louse,  Troctes  divinatoria  Mull,  (a  member  of  the  order  Corroden- 
tia,  family  Psocidse)  and  a  common  hen  louse,  Menopon  hiseriatum 
Piaget  (a  member  of  the  order  Mallophaga),  leads  us  to  believe  that  the 
parasitic  Mallophaga  have  been  derived  directly  from  the  Psocidse. 
Knowing  the  habits  of  the  book  louse,  we  can  easily  imagine  how  the 
line  of  parasitism  might  eventually  have  become  established ;  i.e.  from 
the  eating  of  feathers,  skins  and  excretions  off  the  animal  to  the  eat- 
ing of  the  same  07i  the  animal  as  a  host  is  not  difficult  to  imagine  at 
least. 

Degrees  of  parasitism  may  also  be  illustrated  by  examples  from  the 
biting  lice  (Mallophaga,  in  which  there  are  species  having  the  power  to 
run  freely  and  live  for  a  considerable  length  of  time  off  the  host,  e.g. 
Menopon  pallidum  Nitzsch.,  the  common  hen  louse,  while  other  related 
species  have  become  quite  sessile,  as  in  the  extreme  case  of  the  worm- 
like louse  (Menopon  titan  Piaget),  inhabiting  the  gular  pouch  of  the 
pelican.  Among  the  fleas  there  are  also  good  examples  of  gradation  in 
habit  and  structure,  e.g.  the  human  flea  {Pulex  irritans  Linn.),  which 
has  developed  remarkable  springing  power  and  is  comparatively  free  to 
move  from  place  to  place,  while  the  mature  female  hen  flea  (Echidnophaga 
gallinacea  Westw.)  is  usually  quite  sessile,  holding  fast  to  one  point  much 
like  a  tick. 

Systematic  Position  of  Animal  Parasites.  —  Though  parasitic  animal 
organisms  are  found  in  other  phyla,  those  affecting  man  and  beast  are 
included  almost  exclusively  in  the  following : 

a.  Protozoa, — unicellular  animals  (Fig.  1) ;  e.g.  Entamoeba  histolytica  Schaudinn, 
causing  amoebic  dysentery ;  Plasmodium  viva.t  Grassi  and  Feletti,  caus- 
ing malaria ;  Trypanosoma  gambiense  Button,  causing  African  sleeping 
sickness. 

6.  Nemathelminthes,  —  bilateral,  unsegmented  worms  of  cylindrical  form  (Fig, 
2) ;  e.g.  Trichinella  spiralis  Owen,  causing  trichinosis ;  Ascaris  lumbri- 
coides,  roundworm  of  man ;  Ankylostoma  duodenale  Dubini,  a  hookworm 
of  man.     Development  is  us  ually  direct. 


PARASITES  AND   PARASITISM 


9 


c  Platyhelminthes,  —  h-i\eitera\  worms;  flattened  dorsoventraUy ;  no  anal 
opening.  Usually  requiring  an  intermediate  host. 
1.  Cestoda,- head  or  scolex  with  separable  segments  called  proglottides 
VFig  3) ;  e.q.  Toenia  solium  Linn.,  the  pork  tapeworm  of  man ;  Iwma 
saginata  Goeze,  the  beef  tapeworm  of  man;  DivyMvum  camnum 
Linn.,  a  common  tapeworm  of  the  dog. 


Fig.  1. — Types  of  Protozoa.  A.  Sarcodina,  rep- 
resented by  Entamoeba  histolytica  of  Tropical 
Dysentery;  B.  Mastigophora,  represented  by 
Trypanosoma  gambiense  of  African  Sleeping 
Sickness  ;  C.  Infusoria,  represented  by  Balan- 
tidium  coli,  causative  organism  of  a  certain 
oriental  dysentery  (redrawn  after  Leuckart)  ; 
D.  Sporozoa,  represented  by  (a).  Coccidium 
oviforme  from  liver  of  rabbit,  (6)  Plasmodium 
vivax  of  Malaria  shown  in  a  red  blood  corpuscle. 
(All  greatly  enlarged.) 


Fig.  3.  —  Examples  of  parasitic 
flat  worms  (Phylum  Platyhel- 
minthes,  Class  Cestoda.  A 
poultry  tape  worm  {Drepani- 
dotxnia  infundibuliformis 

X  1)  on  the  left;  and  a  com- 
mon tape  worm  of  cattle 
{T.vnia  cxpansa,  greatly  re- 
duced) on  the  right. 


Fig.  2.  —  Examples  of 
parasitic  round  worms 
(Phylum  Nemathel- 
minthes,  Class  Nema- 
toda).  a.  Round 
worm  of  swine  {Ascaria 
suiim)  X  .3 ;  b.  Tri- 
chinella  spiralis  (after 
Leuckart),  greatly  en- 
larged ;  c.  Hookworm 
of  man  {Ankylostomu 
duodenale)  X  1.25. 


Fig.  4.  —  Example 
of  parasitic  flat 
worms  (Phylum 
Platyhelminthes, 
Class  Trematoda) . 
A  liver  fluke  of 
cattle  (Distomum 
americanum)   X  1. 


2.  Trematoda,  —  alimentary   canal   branched;    mouth   in   a   sucker;    e.g. 
Fasciola  hepatica  Linn.,  the  sheep  liver  fluke  (Fig.  4). 


10 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


d.   Annelida,  —  bilaterally  sj-mmetrical,  segmented  or  annulated  womis. 

1.  Choctopoda,  —  locomotor  chatse ;  segmentation  extending  to  internal 
organs,  e.g.  Lnmhricns  terrestris  Linn.,  a  common  earthworm  (non- 
parasitic) (Fig.  5). 


Fig.  5.  —  Example  of  seg- 
mented cylindrical  worms 
(Phylum  Annelida,  Class 
Chsetopoda).  Earth- 

worm {Lumhricus  sp.,  X  .5) 
non-parasitic,  but  may 
serve  as  an  intermediary 
host  for  certain  poultry 
tapeworms. 


Fig.  6.  —  Example  of 
segmented  cylindrical 
worms  (Phylum  Annel- 
ida, Class  Hirudinea). 
Leech  (Hirudo  medi- 
cinalis)    X  .5. 


2.  Hirudinea,  —  flattened ;  sucker  at  each  end  of  body ;  arrangement  of  in- 
ternal organs  does  not  correspond  to  external  segmentation ;  e.g.  Hirudo 
medicinalis  Linn.,  the  medicinal  leech  (Fig.  6). 

Arthropoda,  —  segmented  body  with  jointed  appendages;  exoskeleton; 
bilateral  symmetry ;  ventral  nerve-cord  ; 


Fig. 


7.  —  Examples  of  the  Phylum  Arthropoda,  Class  Crustacea,     a.  Shrimp   Xl.2; 
6.  Crayfish   X  .6  ;   c.  Sowbug   X  2.      (AH  three  examples  are  non-parasitic.) 


PARASITES  AND   PARASITISM 


11 


1.  Crustacea,  —  aquatic;  gill  respiration ;  two  pairs  of  antennae ;  biramous 
appendages ;  e.g.  the  shrimp,  the  crayfish  and  the  sow  bug.  (These 
examples  are  non-parasitic.)     (Fig.  7.) 


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••^'Stl-i 

5- 

^jB^'. 

•   *^'iB  ^'■■ 

tsawKt-L^-, 

1 
r 

(.-^Wb  L. 

,f^u^^B  c . 

r 

r^VV^i 

r 

'^•^             ^ 

^ 

Fig.  8.  —  Example  of  the 
Phylum  Arthropoda,  Class 
Protracheata.  Peripatus 
(after  Folsom)    X  -5. 


Fig.  9.  —  Examples 
of  the  Phylum 
Arthropoda,  Class 
Myriapoda.  a.  A 
centipede  X  .5  ;  h. 
A  millipede    X  .7. 


Protrachentn,  —  elongate,  wormlike,  segmented  body ;  paired,  unseg- 
mented  appendages ;  one  pair  of  antenna; ;  tracheal  respiration ; 
elongate  dorsal  heart;   e.g.  Peripatus  (Fig.  8)  (non-parasitic). 

Myriapoda,  —  body  elongate  and  wormlike ;  each  segment  except  first  two 
and  last  one  bearing  one  pair  of  jointed  walking  appendages.  Centipedes, 
some  of  which  are  venomous  (Fig.  Oo) ;  or  two  pairs.  Millipedes  (Fig.  96). 


Fig.  10.  —  Examples  of  the  Class  In- 
secta.  a.  A  Reduviid  (cone  nose) 
X  1;  b.  A  mosquito  (Anopheles)  X'2  ; 
c.  Bed  bug  (Ciinex)    X  2.5. 

4.  Insecta,  —  body  divided  into  three  divisions  (head,  thorax  and  abdomen) ; 
three  pairs  of  walking  appendages  on  thorax;  two  pairs  of  wings  on 
thorax  (may  be  reduced  or  absent) ;  one  pair  of  antenna? ;  compound 
eyes ;  usually  three  simple  eyes ;  tracheated  respiratory  sj^stem ;  e.g. 
Conorhinus  protractus  Uhler  (cone-nose) ;  Cimex  ledularius  Linn. 
(bed-bug) ;  Anopheles  maculipennis  Meig.  (malaria  mosquito) ;  etc. 
(Fig.  10). 


12 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


Arachnida,  —  head  and  thorax  fused  to  form  cephalothorax ;  four  pairs 
of  walking  appendages  on  cephalothorax  (larvje  may  be  hexapod) ; 
wingless ;  no   antenna? ;  eyes  simple,   when  present ;  e.g.   Latrodectes 


Fig.  11.  —  Examples  of  the  Phylum 
Arthropoda,  Class  Arachnida.  a.  A 
spider  X.5;  b.  A  tick  X  1.3  ;  c.  A 
mite   X  30. 


mactans  Fabr.,  a  poisonous  spider;  Hadrurus  hirsutus  Wood,  scorpion; 
Margaropus  annulatus  Say,  the  Texas  fever  tick ;  Dermanyssus  gallinoe 
Redi,  the  poultry  mite ;  Psoroptes  communis  Furst,  the  scab  mite. 
(Fig.  11). 


CHAPTER  III 
INSECT  ANATOMY  AND   CLASSIFICATION 


Fig.  12. — -A  few  tracheal  tu- 
bules taken  from  an  insect. 
(Greatly  enlarged.) 


The  Insecta  (Fig.  10)  are  essentially  segmented  animals,  the  prim- 
itive number  of  segments  being  probably  nineteen  or  twenty,  based  on 
ontological  evidence.  This  number  is  no  longer  evident,  owing  to  the 
specialization  of  the  head  and  posterior  terminal  segments.  The  most 
striking  condition  is  the  separation  of  the  body  into  three  divisions ;  the 
head  bearing  the  antennae,  mouth  parts  and 
eyes;  the  thorax  possessing  the  locomotor 
appendages,  usually  two  pairs  of  wings  and 
three  pairs  of  legs ;  the  abdomen,  bearing  no 
appendages  except  the  terminal  organs  of 
sexual  prehension  in  the  male,  or  ovipositor  in 
the  female.  The  respiratory  system  of  the 
insect  consists  of  a  complex  series  of  tubes 
(Fig.  12)  ramifying  all  parts  of  the  body, 
carrying  air  from  the  outside  through  the 
spiracles  segmentally  arranged  on  both  sides 
of  the  thorax  and  abdomen. 
^v^'  Insect  Larvae.  — When  insect  larvse,  para- 
sitic or  accidental,  are  encountered  in  the 
body  of  man  or  beast,  there  may  be  some  difficulty  in  classifying  them 
readily,  with  the  result  that  they  may  be  incorrectly  placed  among  the 

worms,  for  example,  bots  and  warbles 
(Qjlstridse),  or  screw  worms  (Chrysom- 
yia)  or  other  flesh  fly  larvae  in  cases  of 
intestinal  myiasis.  Usually  these  larvse 
(Fig.  13)  are  short  and  plump,  ordinarily 
possessing  eleven  or  twelve  well-marked 
segments.  Furthermore,  microscopic  ex- 
amination will  reveal  a  system  of  minute 
tubules  (Fig.  12),  the  tracheal  breathing 
system,  ramifying  all  internal  parts  of 
the  body,  even  the  minutest  portions 
between  muscle  fibers.  This  system  is 
not  present  in  worms. 
The  larvse  of  Dipterous  insects  (flies)  are  commonly  called  "mag- 
gots "  and  are  footless ;  the  larvse  of  Coleoptera  (beetles)  are  called 
"  grubs,"  and  have  three  pairs  of  feeble  legs  ;  the  larvse  of  Lepidoptera 

13 


Fig.   13.  —  Insect   larvse,  —  showing 
typical  external  segmentation.    XI. 


14 


MEDICAL  AND   \^TERINARY  ENTOMOLOGY 


(moths  and  butterflies)  have  never  less  than  four  pairs  of  legs  including 
prolegs  and  are  Imown  as  "caterpillars"  ;  Xeuropterous  larvte  (dobson 
flies,  etc.)  are  not  easily  distinguished,  but  the  presence  of  three  pairs 
of  legs  with  more  than  twelve  body  segments,  including  the  head,  will 
serve  to  distinguish  these  in  at  least  many  cases. 

Importance  of  Knowing  Internal  Anatomy.  —  It  is  important  that 
the  student  familiarize  himself  with  the  internal  anatomy  of  the  insect, 
with  special  reference  to  the  digestive  system  and  its  accessory  struc- 
tures, such  as  the  salivary  glands.  Two  cases  will  point  out  this 
necessity : 

1st.  The  simplest  condition  in  which  the  internal  organs  of  insects 
are  concerned  in  disease  transmission  is  in  the  case  of  the  house  fly,  in 
which  pathogenic  organisms  are  sucked  up  with  dejecta  and  are  passed 
out  with  the  feces  of  the  fly,  and  deposited  on  human  food,  either  in 
their  original  virulent  condition  or  more  or  less  attenuated  or  weakened. 

2d.  The  more  complicated  condition  is  in  the  case  of  the  Anopheles 
mosquito,  which  sucks  up  pathogenic  organisms  (malaria  parasites) 
with  the  human  blood,  and  these  undergo  very  important  and  vital 
sexual  changes  within  the  body  of  the  insect,  eventually  finding  lodg- 
ment in  the  salivary  glands  of  the  same  before  introduction  by  the 
"  bite  "  into  the  next  human  victim,  —  thus  the  insect  is  an  essential 
intermediary  host. 

Digestive  System.  —  There  are  three  distinct  regions  to  the  insect 
intestine  (Fig.  14) ;  namely,  (1)  the  fore-gut,  consisting  of  the  mouth, 
pharynx,  esophagus  and  proventriculus ;  (2)  the  mid-gut,  consisting 
of  the  stomach;    and  (3)  the  hifid-gut,  consisting  of  the  ileum,  colon, 


Fig.  14.  —  Drawing  of  a  typical  insectan  alimentary  tract,  a.  fore-gut ;  b.  mid-gut ;  c.  hind- 
gut;  1.  pharynx  ;  2.  oesophagus;  3.  crop  ;  4.  gizzard  ;  5.  hypopharynx ;  6.  mandibles; 
7.  stomach;  8.  ileum  ;  9.  colon  ;  10.  rectum  ;  11.  anus;  12.  gastric  cseca  ;  13.  Mal- 
pighian  (excretory)  tubules  ;  14.  salivary  gland  ;  15.  salivary  duct.  X  2.  (Adapted 
after  Folsom.)  ^  ' 


rectum  and  anus.  The  proventriculus  presents  merely  a  widened 
portion  of  the  esophagus  in  the  more  generalized  forms  and  serves  as  a 
food  receptacle.  In  the  more  specialized  groups,  such  as  the  Diptera 
and  Lepidoptera,  the  crop  is  expanded  into  a  capacious  pocket  or  pouch. 
In  such  forms  in  which  the  gizzard  is  present  this  organ  consists  of  a 
highly  muscular  dilation  provided  internally  with  chitinous  teeth  for 
grinding  food ;  for  example,  the  grasshopper.     The  stomach  is  a  simple 


INSECT   ANATOMY  AND   CLASSIFICATION 


15 


Fig.  15.  —  Salivary  system  (right  side)  of  an 
insect, — a  cockroach.  1.  SaUvary  glands; 
2.  Salivary  duct ;  3.  Common  salivary  duct ; 
4.  Hypopharynx ;  5.  Reservoir.  (Adapted 
after  Miall  and  Denny.) 


sac  into  which  open  the  gastric  cceca,  generally  few  in  number,  which  give 
rise  to  certain  digestive  fluids.  At  both  ends  of  the  stomach  are  located 
valves  which  direct  the  flow  of  the  food.  There  is  much  variation  in  the 
length  and  degree  of  convolution  of  the  hind  intestine,  but  usually  the 
three  regions  mentioned,  namely,  ileum,  colon  and  rectum,  may  be 
located.  Emptying  into  the  ileum  are  the  excretory  or  Malpighian 
tubules  varying  in  number  and  length  in  the  various  groups  of  insects. 

The  salivary  system  consists 
of  a  pair  of  salivary  glands 
(Fig.  15)  which  may  be  lobed, 
situated  within  the  head,  often 
extending  into  the  thorax. 
Usually  each  gland  empties  into 
a  salivary  duct,  the  two  ducts 
joining  into  a  common  duct 
which  opens  into  the  esophagus 
or  pharynx.  In  many  species 
of  insects  there  is  present  a  pair 
of  salivary  reservoirs ;  these  may 
be  located  near  the  opening  of 
the  common  duct  and  then  pre- 
sent a  compound  condition,  or  may  be  situated  on  either  side  of  the 
esophagus  at  the  end  of  a  long  slender  duct. 

Insect  Classification.  —  The  INIedical  Entomologist  must  be  equipped 
with  a  good  knowledge  of  the  basic  principles  of  classification,  so  as  to  be 
able  to  correctly  place  the  insect  at  hand  in  its  proper  order  and  family  at 
least,  and  in  the  case  of  parasitic  insects  should  be  able  to  run  the  speci- 
men to  the  species  with  the  aid  of  a  key.  To  determine  the  Order  to  which 
an  insect  belongs  one  need  usually  only  know  the  character  an4  structure 
of  the  wings  when  present  and  the  type  of  the  mouth  parts.  This  will  en- 
able the  student  to  place  at  least  ninety  per  cent  of  the  commoner  insects 
in  their  proper  Orders.  Unfortunately  the  parasitic  forms  have  under- 
gone many  changes  such  as  reduction  or  loss  of  the  wings  and  great  modi- 
fication in  form,  but  generally  the  mouth  parts  will  serve  as  a  ready  means 
for  rough  identification.  Before  passing  on  to  a  list  of  the  Orders  of 
insects,  the  usual  basis  for  classification  will  be  considered  here,  viz. :  — 

1.  Wings,  —  (a)  presence  or  ab- 
sence of,  (6)  form,  (c)  structure. 

2.  Mouth  parts,  —  (a)  biting 
(mandibulate),  (6)  sucking  (haus- 
tellate) . 

3.  Metamorphosis,  —  (a)  primi- 
tive,   (6)    simple    (incomplete),    (c) 

Fig.   16.  —  Hypothetical    type    of    wing  „„^„ip„    /'r.nmnlptp'l 

venation.       A.  anal    vein;     C.  costa ;  COmpiCX    (^Complete;. 

Cu.   cubitus;    M.   media;    R.   radius;  WingS.  — ^  The      earliest      SystcmS 

Sc.  subcosta.    (Redrawn  from  Folsom,  «  .            ,      i        -n      j.'                      -l          i 

after  Comstock  and  Needham.)  ot  msect  classification  WCrC  bascd  OU 


16 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


wing  characters,  which  together  with  the  mouth  parts  offer  a  basis  for 
the  more  modern  arrangement  also.  The  venation  of  insect  wings  is 
so  markedly  characteristic  for  each  species  that  even  a  part  of  a  wing  is 


1st  vein 


Fig.  17.  —  Wing  of  an  insect'(Tabanus),  to  illustrate  terminology  as  applied  to  venation 
and  cells. 


often  all  that  is  necessary  for  determination.  There  are  typically  two 
pairs  of  wings  present,  situated  on  the  mesothorax  and  metathorax, 
though  in  many  parasitic  insects,  such  as  the  bedbugs,  lice,  fleas,  cer- 
tain louse  flies,  etc.,  the  wings  are 
absent.  Wingless  insects  such  as 
those  mentioned  should  not  be  in- 
cluded with  the  Aptera,  which  is  an 
order  of  'priviitmely  wingless  insects. 
The  parasitic  wingless  insects  fall 
under  several  different  orders,  as 
will  be  seen.  To  avert  confusion  it 
is  therefore  probably  better  to  dis- 
pense with  the  term  Aptera  and 
substitute  the  term  Thysanura  as 
used  by  a  number  of  entomologists. 
In  form  the  wing  presents  a 
more  or  less  triangular  appearance. 
Generally  the  fore  and  hind  wings 
differ  considerably  in  size ;  the  fore 
wing  in  some  groups,  such  as  the 
May  flies,  many  butterflies  and 
moths,  and  the  bees  and  wasps,  is 
larger  than  the  hind  wing,  while 
in  the  grasshoppers,  cockroaches, 
beetles,  etc.,  the  fore  wing  is  narrow 
and  serves  largely  as  a  cover  (elytron)  to  the  hind  wing,  which  folds 
lanlike.     Again,  in  the  dragon  flies,  white  ants  and  ant  lions,  the  fore 


Fig.  18.  —  Illustrating  primitive  meta- 
morphosis, a.  young  of  a  Thysanuran 
insect  (Campodea) ;  h.  adult  of  the 
same.      (After  Kellogg.) 


INSECT  ANATOMY  AND   CLASSIFICATION 


17 


and  hind  wings  are  nearly  equal.  In  the  flies,  the  hind  pair  of  wings  is 
replaced  by  club-shaped  organs  known  as  halteres,  leaving  consequently 
only  one  pair  of  wings,  hence  the  name  Diptera  (two-winged). 

There  is  also  a  great  variation  in  structure  of  the  wings,  though 
for  each  order  a  certain  general  condition  prevails ;  e.g.  the  Neuroptera 
have  thin  membra- 
nous wings,  often  quite 
filmy ;  however,  Dip- 
tera and  many  Hem- 
iptera  have  the  same 
texture,  but  possess- 
ing fewer  wing  veins 
and  a  different  vena- 
tion. The  Diptera 
can,  of  course,  be 
readily  distinguished 
by  the  presence  of 
but  a  single  pair  of 
wings.  The  typical 
Hemiptera  have  the 
front  wings  thickened 
at  the  base,  while 
the  apical  portion  is 
membranous  (Hemip- 
tera-Heteroptera). 
The  other  two  divi- 
sions of  this  order, 
one  of  which  has  a 
pair  of  entirely  mem- 
branous wings  (Hem- 
iptera-Homoptera), 
the  other  wingless 
(Hemipt  era-Pa  ra- 
sita),  can  be  readily 
distinguished  on  the 
basis  of  mouth  parts. 

The  venation  of 
the  insect  wing,  as 
has  been  mentioned,  is  an  important  factor  in  classification  on  account 
of  the  great  variety  of  arrangement,  and  the  reliability  of  this  character 
for  identification  of  the  family  and  species.  By  a  careful  study  of  the 
evidence,  a  fundamental  type  of  wing  venation  has  been  constructed  by 
Comstock  and  Needham.  The  figure  (Fig.  16)  illustrating  this  type 
will  be  useful  in  determining  the  identity  of  the  principal  veins.  The 
spaces  between  the  veins  are  called  cells,  shown  in  Fig.  17,  which  figure 
also  illustrates  the  use  of  the  numerical  system  of  nomenclature. 


Fig 


19.  —  Illustrating  simple  metamorphosis.  a.  Young 
wingless  grasshopper  ;  b.  Showing  wing  pads  after  the  first 
molt ;    c.  Adult  of  the  same.     (Redrawn  after  Packard.) 


18 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


Metamorphosis.  —  In  order  to  attain  to  the  size  and  development 
of  the  parent  the  young  insect  undergoes  greater  or  less  change  in  size, 
form  and  structure,  which  series  of  changes  is  termed  metamorphosis. 
The  least  change  is  found  in  the  Thysanura  (Aptera),  which  are  primi- 
tively wingless,  and  hence  the  newly  emerged  young  individual  is  ex- 
ternally unlike  the  parent  only  in  size,  —  this  type  of  metamorphosis 
is  termed  yriinitive  (Fig.  18). 

A  greater  difference  is  found  in  the  young  and  adult  grasshopper 
(Fig.  19).  Other  than  the  difference  in  size  and  sexual  maturity  the 
absence  of  wings  in  the  young  is  at  once  apparent.  In  order  to  reach 
the  winged  condition,  the  young  individual  molts  at  intervals,  and  with 
each  molt  secures  longer  wings  until  after  a  definite  number  of  molts 
the  fully  developed  wings  are  present.  The  following  stages  may  be 
recognized:  (1)  egg,  (2)  nymph,  (3)  imago  (not  sexuaily  mature)  and 
(4)  adult  or  sexually  mature  individual.  This  type  of  metamorphosis 
is  termed  simple  or  incomplete. 

The  greatest  difference  between  the  newly  hatched  young  and  the 
parent  occurs  in  such  forms  as  the  house  fly  (Fig.  20),  the  butterfly, 


Fig.  20.  —  Illustrating  complex  metamorphosis.     Life  history  of  the  common  housefly. 
a.  egg ;    b.  larva ;    c.   pupa ;   d.  adult. 


etc.  In  these  forms  the  newly  emerged  young  individual  has  no  re- 
semblance whatever  to  the  adult,  having  the  appearance  of  a  seg- 
mented worm.  (Of  course,  the  internal  anatomy  and  certain  other 
features  are  distinctly  insectan.)  The  fact  that  the  young  are  man- 
dibulate  and  the  adults  haustellate  in  Diptera  and  Lepidoptera  offers 
much  interesting  ground  for  ecological  discussion,  but  is  out  of  order 
at  this  time.     In  order  to  attain  the  winged  condition  of  the  adult 


INSECT  ANATOMY  AND   CLASSIFICATION  19 

from  the  wingless,  wormlike  condition  of  the  young,  many  profound 
changes  must  be  undergone  and  a  new  stage  is  entered,  the  pupa,  or  rest- 
ing stage,  in  which  this  transformation  is  accomplished.  The  newly 
emerged  young  insect  is  called  the  larva,  and  we  have  consequently  the 
following  stages  to  deal  with :  (1)  egg,  (2)  larva,  (3)  pupa,  (4)  imago, 
(5)  adult.     This  type  is  termed  complex  or  complete  metamorphosis. 

External  Anatomy.  —  In  order  to  familarize  himself  with  the  external 
anatom\'  of  insects,  especially  with  the  parts  upon  which  classification 
is  mainly  based,  the  student  should  study  carefully  some  hard-bodied 
insect  of  a  generalized  nature.  Such  an  insect  need  not  be  a  parasite, 
indeed,  the  author  prefers  that  a  non-parasitic  form  be  used  because 
there  is  less  specialization.  The  common  grasshopper  answers  the 
purpose  very  well,  and  a  careful  study  of  Fig.  21  is  recommended. 

Keys  to  Classification.  —  The  student  is  now  prepared  to  better 
understand  the  use  of  a  key  to  classify  any  insect  at  hand.  The  first 
thing  he  needs  to  do  is  to  place  the  insect  in  its  proper  order,  which  may 
be  done  with  the  aid  of  the  following  key.  While  the  use  of  a  key  in 
classification  of  animals  may  seem  to  be  essential,  the  student  should 
not  become  a  slave  to  this  very  mechanical  method  of  placing  creatures 
in  their  proper  class,  order  or  family. 

Key  to  the  Orders  of  Insects  ^ 

A.  Primitive  wingless  insects;  mouth  -parts  well  developed,  but  all  except  the  apices 
of  the  mandibles  and  maxillce  withdrawn  into  a  cavity  in  the  head;  tarsi 
(feet)  always  one  or  two  clawed ;  body  sometimes  centipede-like,  with 
well-developed  abdominal  legs,  in  this  case  tarsi  two-clawed  —  (the 

simplest  insects) APTERA 

A  A.   Normally  winged  insects,  wings  sometimes  rudimentary  or  absent ;  mouth 
parts  not  withdrawn  into  a  cavity  in  the  head. 

B.  Mouth  parts,  when  developed,  with  both  mandibles  and  maxillce  fitted 
for  biting;  abdomen  broadly  joined  to  thorax;  tarsi  never  bladder- 
shaped;  when  mouth  parts  are  rudimentarj' ,  if  the  wings  are  two, 
there  are  no  halteres ;  if  the  wings  are  four  or  absent,  the  body  is 
not  densely  clothed  with  scales. 

C.  Posterior  end  of  abdomen  with  a  pair  of  prominent  unjointed 
forceps-like  appendages ;  fore  icings,  when  present,  short  vein- 
less,  horny  or  leathery  —  (Earwigs)  .  EUPLEXOPTERA 
CC.  Posterior  end  of  abdome7i  usually  without  prominent  unjointed 
forceps-like  appendages;  when  these  are  present  the  fore 
wings  are  always  developed,  veined. 

D.  Fore  wings,  when  present,  veined  and  niembranoiis,  parch- 
ment-like or  leathery,  when  absent,  the  labium  (under- 
lip)  either  cleft  in  the  middle,  or  the  mouth  parts  pro- 
longed into  a  distinct  beak. 

E.  Fore  wings,  when  present,  thicker  than  hind  ivings, 
somewhat  leathery  or  parchment-like;  hind  wings 
folded  several  times,  lengthwise,  like  a  fan,  in  repose  ; 
when  wings  are  absent,  prothorax  large  — 
(locusts,  crickets,  cockroaches,  etc.) 

ORTHOPTERA 

^  After  Kellogg  (by  permission)  arranged  by  Professor  H.  E.  Summers. 


20 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


IxNSECT  ANATOMY  AND   CLASSIFICATION  21 

EE.   Fore^  wings  membranous,   of  same  structure  as  hind 
wings;    hind  wings  usually  not  folded;    but  oc- 
casionally folded   like   a  fan;    when   wings   are 
absent,  prothorax  small. 
F.   Antennce  inconspicuous. 

G.  Hind  wings  smaller  than  fore  or  absent; 
posterior  end  of  abdomen  uith  two  or 
three     many-jointed    filaments  —  (May 

flies) EPHEMERIDA 

GG.  Hind  wings  not  smaller  than  fore ;  posterior 
end  of  abdomen  withotd  many-jointed 
filaments  —  (dragon    flies    and    damsel 

flies) ODONATA 

FF.   Antennce  conspicuous. 

G.  Tarsi  less  than  five-jointed ;  labium  cleft 
in  the  middle. 

H.    Wirigs  always  present,  although  some- 
times   very    small;     hind    loings 
broader  than  fore  wings,  folded  in 
repose;     prothorax    large,    nearly 
flat    on   dorsal  surface  —  (Stone 
flies)       .     .     .     PLECOPTERA 
HH.   Hind  wings,  when  present,  not  broader 
than  fore  ivings,  not  folded  in  re- 
pose, prothorax  small,  collar-like. 
I.    Tarsi  four-jointed,  wiyigs  when 
present  equal  in  size  —  (Ter- 
mites)   .     .     .     ISOPTERA 
//.    Tarsi  one  to  three  jointed. 

J.  Tarsi  one  or  two  jointed 
always  ivingless  —  (bit- 
ing lice) 

MALLOPHAGA 
J  J.  Tarsi  usually  three- jointed; 
occasionally  two-jointed, 
in  which  case  wings  al- 
ways present,  fore  wings 
larger  than  hind  wings  — 
(Book  lice,  etc.) 

CORRODENTIA 
GG.    Tarsi  five- jointed,  but  with  07ie  joint  some- 
times   difficult    to    distinguish;     labium 
visually    entire    in    middle,    sometimes 
slightly  emarginate. 

H.    Wirgs,     when    present,     naked    or 

slightly  hairy;  hind  ivings  loith  or 

withotd   folded    anal    space;     in 

former  case  prothorax   large   and 

nearly  fiat  on  dorsal  surface;    in 

wingless   forms  mouth  prolonged 

into  a  distinct  beak. 

/.    Mouth  parts  not  prolonged  into  a 

distinct  beak,  at  most  slightly 

conical  —  (Dobsons,  ant 

lions,  etc.)  NEUROPTERA 


22  MEDICAL  AND   VETERINARY  ENTOMOLOGY 

//.  Mouth  parts  prolonged  into  a  dis- 
tinct beak  —  (Scorpion  flies, 
etc.)      .     .     MECOPTERA 

HH.   Wings,  when  present,  thickly  covered 
with   hairs;    hind   icings   usually 
with  folded  anal  space ;   prothorax 
small,  collar-like;  mouth  not  pro- 
longed  into    a    beak  —  (Caddis 
flies)     .     .     .     TRICPIOPTERA 
DD.   Fore  wi^igs,   when    present,  veinless;     horny   or    leathery; 
when  absent,  labium  entire,  and  mouth  parts  not  pro- 
longed into  a  distinct  l)eak—  (Beetles)   COLEOPTERA 
BB.  Mouth  parts,  when  developed,  more  or  less  fitted  for  sticking;  sometimes 
also  fitted  in  part  (the  mandibles)  for  biting;    in  this  case  either 
(1)  base  of  abdomen  usually  strongly  constricted,  joined  to  thorax 
by  a  narroiv  peduncle,  or  (2)  the  tarsi  bladder-shaped,  without  claws; 
when  mouth  is  rudimentary  either  the  wings  are  two  and  halteres 
are  present,  or  the  wings  are  four  or  none  and  the  body  (and  wings 
if  present)  are  densely  clothed  with  scales. 

C.  Prothorax  free ;  body  {and  wings  if  present)  never  densely  clothed 
with  scales;  maxillary  palpi  usuallj^  absent;  when  present, 
tarsi  bladder-shaped,  without  claws. 

D.    Tarsi  bladder-shaped,  ivithout  claws ;  wings  four  (sometimes 
absent),  narroiv,  fringed  xcith  long  hairs;  maxilhr  trian- 
gular,  with   palpi  —  (Thrips)     .    THYSANOPTERA 
DD.    Tarsi  not  bladder-shaped,  usimlly  clawed;  wings  not  fringed 
ivith  long  hairs  ;  maxilla  {xohen  mouth  is  developed)  bristle- 
like, ivithout  palpi  —  (Bnga)     .     .     .     HEMIPTERA 
CC.   Prothorax  not  free;    maxillary  palpi  present,  sometimes  rudi- 
mentary and  difficult  to  see,  in  which  case  body  (and  wings  if 
present)  densely  clothed  with  scales ;    tarsi  never  bladder- 
shaped,  usually  clawed. 
D.   Mandibles  often  rudimentary,  when  present  bristle-like. 

E.  Wings  four  {sometimes  wanting),  clothed  ivith  scales; 
body  covered  thickly  with  scales  or  hairs;  mouth, 
when  developed,  a  slender,  sucking  proboscis,  closely 
coiled  under  head  —  (Moths  and  l:)utterflies) 

LEPIDOPTERA 

EE.    Wings  two  {or  xcanting),  naked  or  with  scattered  hairs; 

hind  icing  in  winged  forms  represented  by  halteres; 

body  either  naked  or  with  scattering  hairs;   mouth, 

a  soft  or  horny  beak  not  coiled  under  head. 

F.   Prothorax  poorly  developed,  scarcely  visible  from 

dorsal    side  —  (Flies)       .     .     .     DIPTERA 

FF.   Prothorax  well  developed,  distinctly  visible  from 

dorsal   side;    wings   never   present    (Fleas) 

SIPHONAPTERA 

DD.   Mandibles  well  developed,  fitted  for   biting;    wings  foitr 

{sometimes  two  or  none) ,  naked  or  with  scattered  hairs  — ■ 

Clchneumon    flies,    gallflies,    wasps,   bees   and    ants) 

HYMENOPTERA 


CHAPTER  IV 
INSECT  MOUTH    PARTS 

Importance  of  Mouth  Parts.  —  It  is  evident  that  an  insect  possessing 
mouth  parts  capable  of  penetrating  the  skin  of  the  higher  animals  must 
be  looked  upon  as  a  possible  carrier  of  blood  infection,  although  it  may, 


Fig.  22.  —  Head  and  proboscis  of  the  common  house  fly  (Musca  domestica)  on  the  left ; 
the  stable  fly  (Stomoxys  calcitrans)  on  the  right.  Though  close]^  related  systematically, 
the  mouth  parts  of  the  two  species  are  very  different ;  both  are  suctorial,  but  the  former 
cannot  pierce  the  skin  while  the  proboscis  of  the  latter  encloses  piercing  setae  adapted  for 
that  purpose. 

in  actual  experience,  never  attack  such  animals.  If  the  insect  is  pro- 
vided with  mouth  parts  of  the  usual  biting  type  or  is  non-piercing,  it 
cannot  relate  to  the  transmission  of  infection  introduced  into  the  cir- 
culation, except  through  a  previously  inflicted  open  wound. 

23 


24  MEDICAL  AND   VETERINARY   ENTOMOLOGY 

The  mosquito  would  be  harmless  as  far  as  malaria  and  yellow  fever 
are  concerned  if  the  mouth  parts  were  of  the  mandibulate  or  biting  type. 
These  insects  together  with  certain  other  species  such  as  the  stable  fly 
{Stomoxys  cahltrans) ,  the  tsetse  flies  and  the  ticks  are  important  be- 
cause of  the  power  which  they  possess  of  piercing  the  skin  of  higher  ani- 
mals and  thus  introducing  pathogenic  organisms  into  the  blood. 

The  actual  measures  of  control  are  often  dependent  on  a  knowledge 
of  the  mouth  parts  of  the  insect  concerned. 

Classification  of  Mouth  Parts.  —  From  the  standpoint  of  Medical 
Entomology  it  is  not  serviceable  to  divide  insects  into  only  two  general 
groups  based  on  the  mouth  parts,  i.e.,  mandihulata  (biting)  and  haustel- 
lata  (sucking).  This  becomes  evident  when  it  is  considered  that  the 
house  fly  {Musca  domestica)  and  the  stable  fly  (Stomoxys  calcitrans)  both 
have  haustellate  mouth  parts  (Fig.  22),  belong  to  the  same  family 
(Muscidffi),  and  are,  therefore,  systematically  closely  related ;  yet  from 
the  standpoint  of  disease  transmission  differ  widely.  By  virtue  of  the 
piercing  stylets  enclosed  within  the  labium,  the  stable  fly  relates  to  direct 
infection  (inoculation),  while  the  proboscis  of  the  house  fly,  quite  ineffec- 
tive as  a  piercing  organ,  relates  it  to  indirect  infection.  Because  of  the 
deficiencies  of  the  older  systems  of  mouth-part  classification  the  follow- 
ing types  will  be  recognized. 

1.  Orthopteron  type,  —  generalized  mouth  parts  consisting  of  opposable  jaws  used 

in  biting  and  chewing,  as  in  the  grasshopper. 

2.  Physopodan  type,  —  mouth  parts  representing  an  intermediate  type ;    ap- 

proaching the  biting  form,  but  functioning  as  suctorial  organs,  as  in 
the  thrips. 

3.  Hemipteron  type,  — mouth  parts  consisting  of  piercing  suctorial  organs,  com- 

prising three  or  four  stj'lets  closely  ensheathed  within  the  labium,  as 
in  the  cone-nose  and  bedbug. 

4.  Dipteron  type,  ^-  suctorial  organs,  piercing  or  non-piercing ;  no  special  rep- 

resentative is  available   for   the  entire  group  of   Diptera,  hence  the 
following  subtypes  must  be  recognized. 

a.  First    subtype,  —  mosquito ;     mouth  parts    consisting    of    six    piercing 

stylets,  loosely  ensheathed  within  the  labium. 

b.  Second  subtype,  —  horsefly ;   mouth  parts  consisting  of  six  short  blade- 

like structures  used  for  piercing  and  cutting,  all  loosely  ensheathed 
within  the  labium. 

c.  Third    subtype,  —  stable  fl}^ ;    mouth  parts    consisting   of    two  heavy, 

piercing  stylets,  closely  ensheathed  within  the  labium. 

d.  Fourth   subtype,  —  house  fly ;    mouth  parts   consisting   of  a  muscular 

proboscis,  not  suited  for  j^iercing ;   stylets  aborted. 

5.  Hy^nenopteron  type,  —  mouth  parts  consisting  of  suctorial,  lapping  organs, 

mandibles  specialized  for  portage  and  combat,  as  in  the  bee,  wasp  and 
ant. 

6.  Lepidopteron  type,  —  mouth  parts  consisting  of  a  suctorial  coiled  tube,  as  in 

the  cabbage  butterfly. 


INSECT   MOUTH   PARTS 


25 


Morphology  of  Mouth  Parts 

The  Orthopteron  Type.  —  To  illustrate  this  type  either  the  grass- 
hopper or  the  cockroach  may  be  used,  but  since  the  former  is  more  easily 
obtainable  and  can  be  handled  more  satisfactorily,  it  will  serve  this 
purpose  well.  This  type,  the  mandibulate  or  biting,  is  the  generalized 
or  primitive  form  and  will  serve  as  a  basis  for  later  comparisons  and 
derivations.  It  is  not  of  direct  importance  in  relation  to  INIedical  Ento- 
mology excejjt  as 
it  furnishes  a  basis 
for  a  better  un- 
derstanding of  the 
ha  us  tell  ate  or 
sucking  type. 

If  the  head  of 
the  grasshopper 
(Fig.  23)  is  viewed 
from  the  side  and 
again  from  the 
front,  the  relative 
position  of  the 
parts  will  be  bet- 
ter understood. 
Separating  the 
mouth  parts  (Fig. 

24J    01    tne    grass-  Fig.  23.  —  Head  of  a  grasshopper,  to  illustrate  the  relative  posi- 

hoDDer       the     fol-  ^'^'^  °^  head   structures   in   insects.     A.    side   view ;     B.    front 

.     '^^y     '  view.      1.  antennae;   2.   compound  eye ;  3.  ocelli  (simple  eyes)  ; 

lowmg    structures  4.  gena  (cheek)  ;    5.  clypeus;   6.  labrum  ;    7.  palpi ;     8.  labium. 

will    be    observed.  (Redrawn  after  Folsom.) 

In  front,  low  down  on  the  head,  hangs  the  labrum  or  upper  lip,  easily 
lifted  as  one  would  raise  a  hinged  lid,  the  hinge  line  being  at  the  lower 
part  of  the  sclerite  or  plate,  known  as  the  clypeus. 

The  labium  functions  as  does  the  upper  lip  in  higher  animals,  i.e.,  it 
draws  the  food  toward  the  mandibles.  In  this  the  labrum  is  greatly 
aided  by  a  rough  structure  called  the  epipharyn.r,  which  forms  the  inner 
lining  of  the  labrum  and  clypeus.  Because  of  the  close  association  of 
these  two  structures  they  are  often  referred  to  as  a  double  organ,  the 
labrum-epipharynx.  Removing  the  labrum,  a  pair  of  heavy,  black, 
opposable  jaws,  the  mandihles,  is  exposed.  These  are  biting  structures 
par  exceUence.  They  are  toothed  and  movable  laterally,  instead  of  ver- 
tically as  in  the  vertebrates.  Dislodging  the  mandibles  brings  into  view 
the  pair  of  maxillae,  or  accessory  jaws.  These  organs  are  known  as  first 
maxUloe.  They  are  composite  structures  separable  into  cardo,  stipes, 
lacinia,  galea  and  palpus,  which  should  be  carefully  observed,  inasmuch 
as  they  undergo  great  modification  in  the  remaining  types  of  mouth  parts. 
The  two  supporting  sclerites  of  the  maxillae  are  called  the  cardo  (basal) 


26 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


and  stipes  (the  second),  while  the  distal  lobes  are  called  (1)  the  maxillary 
palpus  (a  jointed  structure),  (2)  the  galea  (median  and  fleshy),  (3)  the 
lacinia  (inner  and  toothed,  capable  of  aiding  in  comminuting  food). 


Fig.  24.  —  Mouth  parts  of  a  grasshopper,  typical  mandibulate  structures,  Orthopteron 
type.  a.  labrum ;  b.  mandibles;  c.  maxilla,  consisting  of  (1)  cardo,  (2)  stipes, 
(3)  palpus,  (4)  lacina,  (5)  galea;  d.  labium,  consisting  of  (1)  submentum,  (2)  mentum, 
(3)  palpus,  (4)  ligula ;  e.  hypopharynx  or  tongue. 

Underneath  the  maxillae  and  forming  the  floor  of  the  mouth  lies  the 
lower  lip  or  labium,  a  double  structure  frequently  called  the  second 
maxilla.  On  the  same  plan  as  the  maxillse,  the  labium  consists  of  a 
basal  sclerite,  the  submentum,  followed  by  the  mentum,  upon  which  rest 


INSECT  MOUTH   PARTS 


27 


the  labial  palpi  (a  pair  of  outer  jointed 
structures  to  the  right  and  left),  and  the 
ligula  (a  pair  of  strap-like  plates  which 
together  correspond  to  the  upper  lip).  The 
labium  is  also  subject  to  much  modification 
in  insects. 

The  fleshy  organ  still  remaining  in 
the  mouth  cavity  after  the  parts  just  de- 
scribed have  been  removed  is  the  tongue 
or  hypopharynx,  an  organ  of  taste,  func- 
tionally comparable  to  the  tongue  of  verte- 
brates. 

The  mandibles  are  most  useful  landmarks, 
since  they  are  almost  universally  present  in 
insects,  though  in  various  degrees  of  devel- 
opment from  the  strong  mandibles  of  cer- 
tain beetles  (Lucanidse)  to  the  vestigial 
structures  in  certain  Lepidoptera.  In  the 
Hymenoptera,  even  though  the  order  is  of 
the  haustellate  type,  the  mandibles  are  never- 
theless important  structures,  serving,  for  ex- 
ample, in  the  honeybee  as  wax  implements 
and  organs  of  defense,  and  in  ants  as  organs 
of  portage  and  combat.  In  Hemiptera 
and  Diptera   the   mandibles    are    modified 

into  piercing  organs.     The  maxillse  are  subjected  to  great  modification. 

Though  like  the  first  type,  unimportant  in  its 
z  relation    to    disease    trans- 

mission, this  type,  the 
Physopodan  (Fig.  25),  is 
distinctly  important  phylo- 
genetically  as  a  connecting 
link  between  the  biting 
and  piercing-sucking  mouth 
parts.  It  is  in  the  very 
minute  thrips  (Physopoda) 
that  we  find  a  transitional 
type  of  mouth  parts,  biting 
in  general  structure  but 
sucking  in  function.  The 
parts  are  all  more  or  less 
readily  traceable  to  the 
generalized  Orthopteron 
type,  but  have  become 
considerably    elongated  for 


Fig.  25.  —  Head  and  mouth  parts 
of  thrips,  mandibulate  in  struc- 
ture but  crudely  suctorial  in 
function.  Physopodan  type. 
Front  view  of  head.  (1)  labrum, 
(2)  mandibles,  (3)  maxillae, 
(4)  maxillary  palpi,  (5)  labium, 
(6)  labial  palpi,  (7)  hypophar- 
ynx (?),  (8)  eyes,  (9)  antennae. 
(Redrawn  after  Uzel.) 


Physopodan  Type. 


Fig.  26.  — -  Head  and  mouth  parts  of  a  cone-nose, 
piercing  and  stucorial,  with  jointed  proboscis. 
Hemipteron  type.  A.  side  view  of  head  showing 
(1)  portion  of  antenna,  (2)  compound  eye, 
(3)  ocellus,  (4)  clypeus,  (5)  jointed  labium, 
(6)  protruding  setse  or  piercing  bristles,  consisting 
of  the  mandibles  and  maxillae.  B.  Shows  setae 
withdrawn  from  labium.  (7)  mandibles,  (8)  max- 
illae, (9)  hypopharynx. 

piercing  and   are   suctorial   in  function. 


28 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


Fig.  27.  —  Head  and  mouth  parts 
of  a  mosquito  (Culex  sp.).  Il- 
lustrating the  generalized  Dip- 
teron  type  of  mouth  parts  (first 
subtype)  with  maximum  num- 
ber  (six)  of  bristle-like  stylets. 

(1)  Nematoceran       antennae ; 

(2)  compound  eyes  ;  (3)  elypeus  ; 
(4)  labium  ;  (5)  labella  ;  (6)  man- 
dibles ;  (7)  maxilla ;  (8)  maxil- 
lary palpi;  (9)  labrum ;  (10) 
hypopharynx. 


Hemipteron  Type.  —  A  very  different 
sort  of  organ  than  those  above  described 
is  found  in  the  Hemiptera  (Pig.  26).  Here 
the  labium  forms  a  prominent  beak  which 
is  usually  three  (rarely  one  or  four)  jointed 
and  telescopic.  This  beak  incloses  a  pair 
of  mandibles,  often  provided  with  terminal 
barbs,  and  a  pair  of  maxilla?,  all  stylet-like 
and  of  great  efficiency  in  piercing  the  skin. 
The  maxillpe  are  more  or  less  completely 
joined,  forming  a  tube,  so  that  only  three 
stylets  can  be  seen  on  examination.  The 
labrum  is  quite  short  and  inconspicuous. 

Dipteron  Type.  —  (a)  First  Subtype, 
the  Mosquito.  —  The  most  generalized  type 
of  Dipteron  mouth  parts  is  found  in  the 
mosquito  (Fig.  27),  hence  here  we  find  the 
maximum  number  of  stylets  representing 
the  structures  of  the  more  generalized  type, 
loosely  ensheathed  within  the  elongated 
labium,  the  whole  forming  a  prominent 
beak  or  proboscis.  The  identity  of  the 
six  stylets  is  not  well  established,  though 
it  is  generally  accepted  that  they  represent 
the  two  mandibles,  the  two  maxillae  (dis- 
tinctly serrated  distally),  the  hypopharynx, 
and    the    labrum.-epipharynx.     The   palpi 


Fig.  28.  —  Head  and  mouth  parts  of  a  horsefly  (Tabanus).  The  rnaximum  number  of 
parts  is  retained,  but  the  piercing  structures  are  distinctly  blade-like.  Dipteron  type, 
second  subtype.  A.  Side  view  of  head  showing  (1)  antenna  (brachycerous),  (2)  com- 
pound eye,  (3)  labium,  (4)  labella,  (.5)  maxillary  palpus.  B.  Piercing  structures  ex- 
posed, labium  removed.  (6)  mandibles,  (7)  maxillae,  (8)  hypopharynx,  (9)  labrum- 
epipharynx. 


INSECT   MOUTH   PARTS 


29 


are  conspicuous  structures  in  all  mosquitoes  and  are  useful  as  a  means 
for  identification.  These  represent  the 
maxillary  palpi  of  the  <2;rasshopper,  while 
the  pair  of  flattened  lobe-like  organs 
forming  the  distal  portion  of  the  pro- 
boscis are  said  to  represent  the  labial 
palpi  and  are  called  the  labella. 

(b)  Dipteron  Tiipe,  Second  Subtype,  the 
Horsefly.  —  While  retaining  the  same 
number  of  parts  as  the  mosquito,  this 
subtype  is  distinctly  characterized  by 
its  flattened  blade-like  condition  (Fig. 
28).  That  these  mouth  parts  serve 
primarily  as  cutting  structures  is  evident 
from  the  quantity  of  blood  usually  drawn 
by  the  "  bite  "  of  a  horsefly,  especially 
one  of  the  larger  species  such  as  the  black 
horsefly  {Tahanus  atratus).  The  labium 
is  the  conspicuous  median  portion  loosely 
ensheathing  the  blades  and  terminating 
in  large  labella.  The  mandibles  are  dis- 
tinctly flattened  and  saber-like,  while  the 
ma.i'illce  are  narrower  and  provided  with  conspicuous  palpi.  The 
hypopharynx  and  labrum-epipharynx  are  both  lancet-like.     In  the  male 


Fig.  29.  —  Head  and  mouth  parts 
of  the  stable  fly  {Stonioxys  calci- 
trans).  Stylets  reduced  in  num- 
ber, closely  ensheathed  by  the 
labium.  Dipteron  type,  third 
subtype.  Side  view.  (1)  antenna, 
(2)  compound  eye,  (3)  labium, 
(4)  labella,  (5)  labrum,  (6)  hypo- 
pharynx,  (7)  maxillary  palpi. 


■Jlii 


y/T- 


Fig.  30.  —  Head  and  mouth  parts  of  the  house  fly  {Musca  domestica) .  Piercmg  stylet 
rudimentary.  Muscular  fleshy  proboscis  not  suited  for  piercing  the  skin  of  higher 
animals.  Dipteron  type,  fourth  subtype.  A.  Side  view.  (1)  Antenna,  (2)  compound 
eye,  (3)  labium,  (4)  labella,  (5)  labrum,  (6)  hypopharynx,  (7)  maxillary  palpi; 
B.   Front  view  of  proboscis. 


30 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


these  piercing  parts  are  very  weakly  developed  and  are  not  useful  as 
weapons  of  attack. 

(c)  Dipteron  Type,  Third  Subtype,  the  Stable  Fly.  —  This  subtype 
(Fig.  29)  is  represented  by  a  group  of  flies  in  which  the  mouth  parts  are 
distinctly  specialized  for  piercing,  and  show,  together  with  the  next 
subtype,  to  what  extent  these  structures  may  become  differentiated 
within  the  same  family  of  insects. 

The  proboscis  at  rest  is  carried  at  the  position  of  a  bayonet  at  charge, 
and  is  therefore  provided  with  a  prominent  muscular  elbow  or  knee. 


Fig.  31.  —  Head  and  mouth  parts  of  the  honeybee  {Apis  jnellifera).  Both  types  of  mouth 
parts  well  developed  but  the  mandibles  are  used  chiefly  for  portage  and  modeling. 
(Hymenopteron  type.)  A.  Front  view  of  the  head  showing  (1)  antennse,  (2)  com- 
pound eyes.  (3)  simple  eye,  (4)  labrum,  (5)  mandibles,  (6)  maxillae  (lacinia),  (7)  labium 
(palpi  only),  (8)  hypopharynx  ( ?)  ;  B.  Mouth  parts  removed  to  show  the  parts,  (5)  man- 
dibles, (6)  maxillae  (lacinia),  (7)  labium  (palpi  only),  (8)  hypopharynx  (?),  (9)  bouton, 
(10)  maxillary  palpus,  (11)  mentum,  (12)  submentum,  (13)  cardo,  (14)  stipes. 

This  conspicuous  organ  (the  proboscis)  is  the  labium  terminating  in  the 
labella,  which  are  provided  with  a  complex  series  of  cutting  and  adhesive 
structures.  Within  the  folds  of  the  labium  and  easily  removable  through 
the  upper  groove  lie  two  setae,  the  labrum,  the  uppermost  and  heavier 
stylet,  and  the  hypopharynx,  a  lower  and  weaker  one,  the  two  forming 
a  sucking  tube  supported  within  the  folds  of  the  labium.  The  maxillary 
palpi  are  located  at  the  proximal  end  of  the  proboscis. 


INSECT   MOUTH  PARTS 


31 


(d)  Dipteron  Type,  Fourth  Subtype,  the  House  Fly.  —  Here  (Fig. 
30)  the  prominent  fleshy  proboscis  consists  mainly  of  the  labium,  which 
terminates  in  a  pair  of  corrugated  rasping  organs,  the  labella,  and  is 
attached  in  elbow-like  form  to  the  elongated  head.  The  entire  structure 
is  highly  muscular  and  may  be  either  protruded  in  feeding  or  partially 
withdrawn  while  at  rest.  Lying  on  top  of  the  grooved  labium  is  the  in- 
conspicuous prolonged  spade-like  lahrum,  which  forms,  with  the  hypo- 
pharynx,  a  sucking  tube,  supported  by  the  labium,  which  latter  also  in- 
closes the  salivary  canal.  By  an  examination  of  the  labrum  it  will  be 
seen  that  it  forms  a  kind  of  convex  covering  to  the  concaved  hypopharynx, 
thus  giving  rise  to  a  food  tube.  The  maxilla^  have  evidently  become 
fused  with  the  fleshy  elbow  of  the  proboscis  and  only  the  prominent 
maxillary  palpi  remain. 

Hymenopteron  Type.  —  In  this  type  the  two  general  classes  of 
mouth  structures,  the  Mandibulate  and  Haustellate,  find  a  rather  strong 
development  in  the  same  species,  though  the  mandibles  are  not  in- 
volved in  the  feeding  process.  The  honeybee  (Fig.  31)  serves  as  a 
representative  species.  The  labrum  is  narrow  and  quite  simple,  the 
mandibles  are  easily  distinguishable  and  are  useful  wax  implements. 
In  ants  the  mandibles  are 
highly  efficient  carrying  organs 
and  weapons  of  defense.  The 
maxillae  form  the  lateral  con- 
spicuous wings  of  the  suctorial 
parts ;  the  lacinia  and  galea 
are  fused  and  the  maxillary 
palpi  are  minute.  The  labium 
is  represented  by  the  long 
structures  to  the  right  and  left 
of  the  middle  tube  which  is 
probably  the  hypopharynx. 
The  hypopharynx  terminates 
in  a  spoon-like  labellum  or 
houton  which  completes  the 
lapping  character  of  the  sub- 
type. 

Lepidopteron  Type.  —  This 
type,  represented  by  the  com- 
moner butterflies  and  moths,  is  typically  a  coiled,  sucking  tube  capable 
of  great  elongation.  Taking  the  cabbage  butterfly  {PoaiitLMLgoi)  as  an 
example  (Fig.  32)  the  labrum  is  seen  to  be  greatly  reduced,  the  mandibles 
absent.  (These  may  be  weakly  present  in  the  lower  Lepidoptera.) 
The  maxillae  are  apparently  onlj'  represented  by  the  galeae,  which  by 
close  approximation  of  their  inner  grooved  surfaces  form  the  long  coiled 
proboscis.  The  double  structure  of  the  proboscis  can  be  easily  demon- 
strated by  manipulation.     The  labium  is  represented  by  the  labial  palpi. 


Fig.  32.  —  Head  and  mouth  parts  of  a  butterfly 
{Vanessa  sp.).  (a)  Side  view.  Suctorial,  coiled 
tube,  Lepidopteron  type.  (1)  antennsB,  (2)  com- 
pound eye,  (3)  proboscis,  consisting  only  of  the 
galeae,  (4)  labial  palpus.  (The  labrum  is  not 
visible  in  side  view.)  (6)  Section  of  proboscis 
showing  double  nature. 


32  MEDICAL  AND   VETERINARY  ENTOMOLOGY 

Orders  of  Insects  Arranged  According  to  Mouth  Parts  with  Type 
OF  Metamorphosis  Indicated 

I.    Orthopteron  type}     Biting  or  chewing  mouth  parts. 

1.  Order  Thysanura,  —  Bristletails,  springtails,  et  al.,  mouth  parts  with- 

drawn in  cavity  of  head ;    primitive  metamorphosis. 

2.  Order     Ephemerida,  —  May     flies,  —  mouth   parts   vestigial ;  simple 

metamorphosis. 

3.  Order  Odonata,  — ■  Dragon  flies  and  damsel  flies,  —  simple  metamor- 

phosis. 

4.  Order  Plecoptera,  —  Stone  flies,  —  simple  metamorphosis. 

5.  Order  Isoptera,  —  White  ants,  —  simple  metamorphosis. 

6.  Order  Corrodentia,  —  Book  lice,  et  al.,  —  simple  metamorphosis. 

7.  Order  Mallophaga,  —  Biting  lice,  —  simple  metamorphosis. 

8.  Order  Orthoptera,  —  Grasshoppers,  cockroaches,  etal.,  —  simple  meta- 

morphosis. 

9.  Order  Euplexoptera,  —  Earwigs,  —  simple  metamorphosis. 

10.  Order  Neuroptera,  —  Dobson  flies,  ant  lions,  aphis  lions,  et  al.,  —  com- 

plex metamorphosis. 

11.  Order   Mecoptera,  —  Scorpion  flies,  —  mouth  parts  prolonged   into  a 

beak  with  mandibles  at  the  tip ;  complex  metamorphosis. 

12.  Order    Trichoptera,  —  Caddis    flies    (moth-like) ;     complex   metamor- 

phosis. 

13.  Order  Coleoptera,  —  Beetles,  —  complex  metamorphosis. 

II.   Physopodan  type.     Biting  in  structure  but  sucking  in  function ;  represents 
a  transitional  form  between  the  biting  and  sucking  insects. 

14.  Order  Physopoda,  —  Thrips,  —  simple  metamorphosis. 

III.  Hemipteron  type.     Elongated,  tj^pically  3  or  4  segmented  proboscis  (un- 

segmented  in  the  true  lice),  snugly  enclosing  stylet-like  organs; 
piercing  and  suctorial. 

15.  Order  Hemiptera,  —  Cicadas,    bedbugs,    cone-noses,    et    al. ;    simple 

metamorphosis. 

IV.  Dipteron  type.     Unsegmented  proboscis,  which  may  or  maj^  not  contain 

piercing  stylets. 

16.  Order  Diptera,  —  mosquitoes,  flies,  et  al. ;   complex  metamorphosis. 

a.  First    subtype.  —  The    mosquito,  —  loosely  ensheathed,  piercing, 

delicate,  stylet-like  structures,  six  in  number,  suctorial. 

b.  Second  subtype,  —  The  horse  fly,  —  piercing,  blade-like  structures, 

six  in  number ;  suctorial. 

c.  Third  subtype,  —  The  stable  fly,  —  closely  ensheathed,  piercing, 

heavy,  stylet-like  structures,  two  in  number ;   suctorial. 

d.  Fourth  subtype,  —  The  house  fly,  —  fleshy,  non-piercing  ;  suctorial. 

17.  Order  Siphonaptera,  —  Fleas,  —  piercing  mouth  parts  closely  related 

to  second  subtype  ;  complex  metamorphosis. 
V.   Hytnenopteron  type.     For  feeding  purposes  the  mouth  parts  are  of  a  non- 
piercing,  lapping  type,  but  for  purposes  of  combat  and  portage 
the  mandibles  are  well  developed. 

18.  Order  Hijmenoptera, — Ants,  bees,  wasps,  et  al.;    complex  metamor- 

phosis. 
VI.   Lepidopteron  type.     Proboscis  in  the  form  of  a  greatly  elongated  coiled 
tube ;  non-piercing,  suctorial. 

19.  Order  Lepidoptera,  —  Moths  and  butterflies ;   complex  metamorphosis. 

^  The  term  "Orthopteron"  is  here  merely  applied  to  indicate  a  type  which 
varies  considerably  in  the  Order  Orthoptera. 


CHAPTER  V 
HOW  INSECTS  CARRY  AND  CAUSE   DISEASE  ^ 

Environmental  Considerations.  —  Manifestly  it  is  necessary  to  know 
under  what  environmental  conditions  pathogenic  organisms  naturally 
exist  in  order  to  ascertain  how  the  insect  becomes  infected  and  in  turn 
is  able  to  infect  man  or  beast.  Two  factors  must  be  considered  in  this 
connection,  first,  the  natural  longevity  of  the  pathogenic  organism,  and 
secondly,  the  degree  of  virulence  of  the  same  w^hen  away  from  the  normal 
host.  For  example,  bubonic  plague  is  a  bacterial  disease,  traceable  to 
Bacillus  pestis,  of  which  the  rat  is  an  important  host.  From  this  host, 
fleas  (which  are  provided  with  piercing  and  sucking  mouth  parts)  become 
infected  and  in  the  bodies  of  these  insects  the  bacilli  multiply  and  remain 
virulent ;  now  if  such  infected  fleas  find  their  way  to  human  beings,  these 
latter  in  turn  may  become  infected.  It  may  be  seen  that  certain  environ- 
mental conditions  must  be  considered  in  this  connection ;  namely,  in 
what  part  of  the  body  of  the  rat  are  the  buboes  (plague  lesions)  found, 
and  does  this  correspond  to  the  distribution  of  the  flea  on  the  host ;  and 
if  the  flea  sucks  up  plague  bacilli,  how  long  will  these  remain  virulent ; 
will  this  be  long  enough  for  the  insect  to  leave  its  first  host,  find  and 
infect  a  second  host?  Then  again  the  question  arises  as  to  how  the 
plague  bacilli  are  introduced  into  the  body  of  the  human  being.  Is  the 
flea  the  only  means  of  dissemination?  These  are  questions  which,  with 
others,  must  be  answered  for  each  case. 

On  the  other  hand  malarial  fever  is  traceable  to  a  protozoon 
(Plasmodium)  which  cannot  exist  in  a  living  condition  away  from 
the  human  body  except  in  the  Anopheline  mosquito.  Its  normal  envi- 
ronment is  very  restricted.  In  the  human  being  it  is  a  blood  parasite, 
requiring  a  blood-sucking  insect  or  other  mechanical  means  to  extract 
it  together  with  blood.  Manifestly  there  are  many  blood-sucking 
insects  which  could  withdraw  parasitized  blood.  It  has,  however,  been 
abundantly  proved  that  malaria  parasites  cannot  reproduce  sexually 
except  in  the  bodies  of  Anopheline  mosquitoes ;  in  all  other  insects  the 
parasites  perish. 

Similar  examples  involving  environmental  peculiarities  might  be 
cited;  for  example,  in  tuberculosis,  a  bacterial  disease,  the  causative 
organism  {Bacillus  tuberculosis)  occurs  largely  in  a  transmissible  infec- 
tive form  away  from  the  body  in  sputum.     On  the  other  hand  African 

1  Students  not  familiar  with  the  classification  of  bacteria  and  protozoa  are 
referred  to  the  appendix. 

33 


34  MEDICAL  AND   VETERINARY  ENTOMOLOGY 

sleeping  sickness,  caused  by  a  protozoon  {Trypanosoma  gamhiense), 
occurs  both  in  the  blood  of  humans  and  certain  native  animals 
(reservoirs),  and  is  carried  by  a  blood-sucking  fly,  the  tsetse  fly  ;  again, 
anthrax,  a  bacterial  disease  (traceable  to  Bacillus  arithracis),  if  in  the 
pustular  form  may  be  transmitted  by  blood-sucking  flies  of  the  family 
Tabanidffi  (horseflies),  as  well  as  in  other  ways,  while  Texas  cattle 
fever,  traceable  to  a  protozoon  (Babesia  bigemina),  is  transmitted 
solely  by  the  tick,  Margaropus  annulatus,  in  which  infection  is  hereditary. 

These  few  examples  will  serve  to  show  the  necessity  for  having  a 
working  knowledge  of  the  pathogenic  members  of  the  two  great  groups 
of  unicellular  organisms,  namely  the  Bacteria  and  the  Protozoa.  In  gen- 
eral it  may  be  said  that  the  longevity  and  pathogenicity  of  the  Bacteria, 
when  outside  the  host  is  considerably  greater  than  in  the  Protozoa, 
owing  to  the  highly  specialized  environment  required  by  the  latter. 

How  Insects  Carry  Disease.  —  The  simplest  way  in  which  insects 
enter  as  a  factor  in  the  transmission  of  disease  is  by  means  of  soiled  feet 
and  mouth  parts.  Any  insect  might  accidentally  become  contaminated 
with  infective  sputum  or  fecal  matter  and  in  turn  might  accidentally 
come  in  contact  with  human  foods,  thus  becoming  an  indirect  factor  in 
transmission.  In  this  connection  the  normal  habit  of  the  insect  must 
be  considered,  i.e.  its  breeding  habits,  food  habits  and  general  behavior. 
Thus  the  house  fly  enters  as  a  factor  in  the  transmission  of  such  diseases 
as  typhoid  fever  and  dysentery,  because  of  its  naturally  filthy  habits. 

A  second  purely  mechanical  method  of  disease  transmission,  though 
more  restricted,  is  by  means  of  a  soiled  piercing  proboscis,  in  cases  of 
certain  parasitic  blood  diseases.  In  the  first-mentioned  method  the 
type  of  mouth  parts  does  not  figure  as  a  restrictive  factor,  but  in  the 
second  method,  in  order  that  the  proboscis  may  become  soiled  with 
blood,  the  mouth  parts  must  be  capable  of  piercing  the  skin^  thus  coming 
in  contact  with  the  blood  and  its  contained  parasites,  if  present.  The 
inoculation  of  the  second  host  may  be  purely  mechanical.  Insects  that 
belong  to  this  class  of  carriers  ordinarily  have  heavy  piercing  mouth  parts 
capable  of  drawing  considerable  blood,  are  intermittent  parasites  and  go 
from  host  to  host  within  a  short  space  of  time.  The  horsefly  (Tabanus) 
is  a  good  representative  of  this  class  in  its  chance  relation  to  anthrax. 

A  more  highly  complicated  method  is  involved  in  the  transmission 
of  bubonic  plague  by  fleas.  In  this  case  the  carrier  has  piercing  mouth 
parts,  is  blood-sucking  and  an  intermittent  parasite.  The  plague  bacilli 
when  taken  into  the  stomach  of  the  flea  multiply  and  do  not  become 
attenuated,  but  pass  out  per  anum  with  the  feces  or  even  in  undigested 
blood;  the  direct  inoculation  is  accomplished  by  a  "rubbing  in" 
process  either  on  the  part  of  the  host  or  flea.  Infection  may  also  take 
place  by  regurgitation  in  the  act  of  biting. 

The  greatest  complexity  is  involved  in  those  cases  in  which  the  insect 
carrier  is  a  necessary  intermediary  host  oj  the  pathogenic  organism,  e.g.  the 
Anopheles  mosquito  in  its  relation  to  malaria.     A  given  period  of  time 


HOW  INSECTS   CARRY  AND  CAUSE  DISEASE  35 

must  elapse  after  the  mosquito  imbibes  infective  blood  before  it  can  trans- 
mit the  causative  organism.  This  period  corresponds  to  the  time 
required  for  the  plasmodium  to  pass  through  its  sexual  cycle  in  the 
stomach  of  the  mosquito  and  find  its  way  into  the  salivary  glands,  ready 
to  be  inoculated  into  the  blood  of  the  mosquito's  next  victim. 

How  Insects  Cause  Disease.  —  Insects  and  arachnids  may  relate 
to  pathological  conditions,  whether  serious  or  of  little  consequence,  in 
one  or  more  of  the  following  ways :  first,  by  direct  infection;  second, 
by  indirect  infection;  third,  by  internal  parasitism;  fourth,  by  external 
parasitism;  and  lastly,  by  venoms.  The  same  species  may  fall  as 
legitimately  into  two  divisions,  as  for  example,  the  Texas  fever  tick, 
which  if  not  infected  with  the  causative  organism  of  the  fever  need  only 
be  considered  as  an  external  parasite,  but  when  the  causative  fever  organ- 
isms are  present  in  the  tick,  would  relate  it  also  to  direct  infection. 

Direct  Infection.  —  Direct  infection  under  ordinary  conditions  could 
only  be  produced  by  an  insect  or  arachnid  possessing  piercing  mouth 
parts,  and  here  no  special  order  or  larger  group  can  well  be  referred  to, 
inasmuch  as  closely  related  insects  may  have  very  different  mouth 
structures.  The  common  house  fly  and  the  stable  fly,  for  example,  belong 
to  the  same  family  (Muscidse),  therefore  are  closely  related,  yet  have 
widely  different  mouth  parts ;  though  both  are  suctorial,  the  former  is 
unable  to  pierce  the  skin,  whereas  the  latter  can  do  so  with  ease. 

B}^  direct  infection  is  meant  the  introduction  of  a  pathogenic  organ- 
ism, whether  bacterial  or  protozoan,  into  the  circulation  of  a  higher 
animal.  The  Anopheles  mosquito  is  therefore  related  to  this  manner 
of  transmission,  because  it  introduces  the  malaria  parasite  (Plasmodium) 
directly  into  the  blood  stream  of  man.  The  same  is  true  of  the  Steg- 
omyia  (iEdes)  mosquito  and  yellow  fever ;  the  Glossina  flies  and  sleep- 
ing sickness ;  horseflies  and  anthrax.  Direct  infectors  are  usually 
temporary,  intermittent  ectoparasites  permitting  transfer  of  activity 
from  animal  to  animal. 

However,  there  is  still  a  possibility  for  an  insect  with  mandibulate 
mouth  parts  or  with  non-piercing  haustellate  mouth  parts  to  infect  an 
animal  as  directly  as  one  possessing  piercing  mouth  parts.  Thus  the 
house  fly  may,  by  means  of  its  feet  and  mouth  parts,  transmit  septicaemic 
infection  to  an  animal  undergoing  surgical  operation  or  suffering  from 
an  open  wound. 

Indirect  Infection.  — •  This  form  of  infection  relates  chiefly  to  enteric 
diseases  in  the  causation  of  which  the  pathogenic  organism  is  deposited 
upon  food  by  the  insect.  Thus  the  food  is  first  infected  and  with  it  the 
pathogenic  organism  is  implanted  within  the  alimentary  canal  of  the 
victim ;  in  this  way  the  insect  is  only  concerned  indirectly.  The  house 
fly,  one  of  the  grossest  transmitters  of  enteric  diseases,  is  only  so  because 
of  accident  of  habit  and  structure,  feeding  as  it  does  indiscriminately 
on  excrement  and  food  of  higher  animals,  and  with  proboscis  and  feet 
so  constructed  as  to  certainly  collect  germ-laden  particles  of  excrement. 


36         MEDICAL  AND   VETERINARY   ENTOMOLOGY 

Insects  possessing  mouth  parts  not  adapted  to  piercing  the  skin 
(whether  biting  or  sucking)  may  relate  to  this  form  of  infection,  and 
indeed  any  insect  or  arachnid  may  be  an  indirect  carrier  by  accident. 
Furthermore,  insects  ordinarily  relating  only  to  indirect  infection  may 
produce  direct  infection  of  certain  kinds  where  there  is  access  to  an  open 
wound  as  already  explained. 

Internal  Parasitism.  —  There  are  no  insects  so  far  as  is  known 
which  spend  their  entire  life  history  in  the  form  of  internal  parasites. 
There  are,  however,  a  number  which  pass  their  larval  period  (period  of 
growth)  within  the  alimentary  canal  or  in  the  muscle  tissue  of  higher 
animals.  The  best-known  representatives  of  this  group  are  the  botflies 
and  the  warble  flies,  the  former  found  in  the  stomach  and  intestine  of 
equine  animals,  while  the  latter  are  found  in  the  muscle  tissue  of  bovine 
and  equine  animals,  rodents,  and  sometimes  man.  The  harm  done  by 
internal  insect  parasites  is  of  various  kinds,  e.g.  irritation,  impaired 
digestion,  loss  of  nutrition,  etc. 

External  Parasitism.  —  The  most  important  and  most  abundant 
external  parasites  of  man  and  of  the  domesticated  animals  are  found 
among  the  insects  and  arachnids.  Very  serious  and  often  fatal  results 
are  due  to  this  form  of  irritation,  and  the  loss  of  blood  due  to  an  abun- 
dance of  blood-sucking  species  must  not  be  overlooked.  External 
parasites  may  be  either  permanent  or  temporary  in  relation  to  the 
host.  The  commonest  permanent  parasites  are  the  biting  and  sucking 
lice,  which  are  usually  transferred  from  host  to  host  by  close  association 
of  mammals  while  sleeping  together  in  close  quarters,  or  while  in  copu- 
lation ;  in  poultry  generally  while  roosting.  The  sucking  lice  are  also 
important  disease  vectors,  which  involves  transfer  of  activity  from 
animal  to  animal,  usually  brought  about  by  close  association,  inter- 
change of  garments  and  toilet  articles.  Thus  lice  are  carriers  of 
typhus  fever  and  relapsing  fever,  infection  being  brought  about  by  the 
bite  or  by  crushing  the  parasites  and  scratching  or  "  rubbing  in  "  the 
infective  agent.  Temporary  intermittent  ectoparasites  are  the  most 
important  of  all  disease  carriers,  owing  to  their  habit  of  changing  hosts. 
It  may  well  be  seen  that  herein  lies  the  danger  of  transmitting  infec- 
tious diseases  from  animal  to  animal.  The  temporary  ectoparasites  are 
well  represented  by  the  fleas,  bedbugs  and  certain  ticks. 

Insect  Venoms.  —  Another  form  of  irritation  is  produced  by  the 
introduction  of  a  specific  venom  by  contact,  pierce  or  sting.  Many 
insects  produce  severe  irritations  by  their  bites,  which  fact  can  be  ac- 
counted for  by  the  presence  of  a  venom-secreting  gland,  often  salivary. 
The  cone-noses  or  kissing  bugs  (Reduviidse)  inflict  a  very  painful  wound 
aggravated  by  a  poison ;  other  insects  produce  nettling  when  handled, 
e.g.  the  blister  beetles  (Meloidse) ;  and  the  familiar  sting  of  the  bee 
(Apidse)  and  wasp  (Vespidse)  is  chiefly  painful  because  of  the  injection 
of  specific  poisons. 


CHAPTER  VI 


COCKROACHES  —  BEETLES  —  THRIPS 
A.   The  Cockroaches 


Order  Orthoptera,  Family  BlattidcB 

Few  insects  excepting  the  lice  are  looked  upon  with  as  much  disgust 
as  are  the  cockroaches.  The  mere  suggestion  that  these  insects  might 
be  present  in  a  dwelling  or  place  of  business  leads  usually  to  a  rough 
snubbing.  Such  is  the  experience  of  inspectors  whose  duty  it  is  to  keep 
a  record  of  vermin  and  noxious  insects  in  connection  with  health  move- 
ments in  certain  cities.  A  flat  denial 
is  often  forthcoming  in  the  face  of 
the  strongest  evidence. 

Habits.  —  Cockroaches  belong  to 
that  group  of  insects  which  attack 
human  food  in  all  degrees  of  prepara- 
tion. Not  only  human  food  but  all 
manner  of  organic  material  is  at- 
tacked ;  nothing  seems  to  be  exempt, 
as  all  will  attest  who  have  spent 
some  time  in  tropical  or  subtropical 
sections  in  particular.  They  are 
omnivorous,  with  a  special  incli- 
nation toward  starchy  and  sugary 
materials.  Where  everything  seems 
to  be  shipshape  during  the  daytime, 
at  night  one  can  hardly  take  a  step 
without  hearing  that  ominous  crackling  underfoot  as  these  creatures 
are  crushed  by  the  tread.  During  the  day  the  cockroaches  are  in 
hiding  in  dark  corners,  behind  wainscoting,  under  boxes,  in  cupboards 
and  the  like,  regardless  (yes,  perhaps  with  predilection)  of  filth. 

Life  History.  —  There  seems  to  be  little  difference  in  the  life  history 
of  the  various  species  of  cockroaches.  The  female  is  often  seen  with  a 
chestnut-colored,  chitinous  object  (Fig.  33),  partly  protruding  from  the 
terminal  abdominal  segment.  This  is  the  egg  case,  or  oothecum,  which 
is  carried  around  by  the  female  often  for  several  weeks  until  the 
young  are  ready  to  hatch.  These  egg  cases  appear  at  all  times  of  the 
year,  hence  it  seems  that  there  is  no   special   season  to  which  egg 

37 


Fig.  33.  - 
roaches, 
ton  bug. 


Egg  cases  (ootheca)  of  cock- 
(o)   oriental  roach ;   (6)   cro- 
X3. 


38 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


deposition  is  limited.     The  young  roaches  are  quite  active  from  the 
beginning,    having    the    same     food     habits    as     the     adults.     Their 


Fig.  34. — The  croton  buf;;  (cockroach),  Blatella  {Ectobia)  germanica,  in  various  stages  of 
development.  The  adult  female  is  shown  with  egg  case  or  oothecum  in  normal  posi- 
tion protruding  from  the  terminal  abdominal  segment.       X  2. 


metamorphosis  is  simple,  quite  like  that  of  the  grasshopper,  requiring 

about  one  year  to  reach  maturity,  prob- 
ably somewhat  less  in  tropical  and 
subtropical  countries.  The  writer  has 
kept  cockroaches  (the  croton  bug) 
under  observation  in  glass  jars  for 
many  weeks  in  order  to  note  their 
growth,  which  was  seen  to  be  very 
slow.  As  the  individuals  molt,  the 
shed  skins  are  eaten,  as  are  also  the 
dead  roaches,  ■ —  an  economical  habit. 
Structural.  —  Cockroaches  have 
characteristically,  dorsoventrally,  flat- 
tened bodies,  generally  of  a  chestnut 
brown  to  black  color.  The  wings  of 
the  males  are  usually  well  developed, 
but  the  females  often  have  mere  ves- 
tiges. While  the  winged  forms  pos- 
sess the  power  of  flight,  the  group  as 
a  whole  is  running  in  habit  and  the 
individuals  can  cover  ground  in  this 
The  mouth  parts  are  of  the  biting 


Fig.  35. 


—  The  oriental  roach,  Blatta 
orientalis.       X  1.3. 


way    with  marvelous  rapidity, 
type,  distinctly  orthopteron. 


COCKROACHES  —  BEETLES  —  THRIPS 


39 


Species  and  Distribution.  —  As  household  pests  cockroaches  are 
widely  distributed,  brought  about  chiefly  through  maritime  trading; 
holds  of  vessels  as  well  as  the  crew's  sleeping  quarters  are  oftentimes  over- 
run with  these  miserable  pests.  The  most  widely  distributed  species 
are  the  croton  bug,  BlateUa  germauica  Linn.  (Fig.  34),  and  the  oriental 
roach,  Blatta  orientalis  Linn.  (Fig.  35).  The  former  is  one  of  the  small- 
est species,  measuring  about  five-eighths  of  an  inch  to  the  tip  of  the 
wings,  which  are  present  in  both  sexes.  This  species  is  evidently  the 
most  common  form  along  the  north  Atlantic  and  north  Pacific  coasts, 
as  shown  by  observations  made  in  Boston,  New  York  and  San  Fran- 
cisco. '  The  name  croton  bug  has 
been  applied  to  this  insect  because  of 
its  appearance  during  the  construc- 
tion of  the  Croton  water  system  of 
New  York  City.  In  color  the  in- 
sect is  a  muddy  brown  with  two 
longitudinal  stripes  on  the  pronotum. 

The  oriental  roach  is  an  inch  or 
more  in  length  and  is  very  much 
darker  than  the  croton  bug,  hence 
is  often  called  "  black  beetle  "  (the 
term  beetle  being  wrongly  applied). 
The  female  has  vestigial  wings,  while 
in  the  male  these  organs  are  short, 
reaching  not  quite  to  the  tip  of  the 
abdomen.  This  form  is  more  com- 
mon in  the  central  states  of  the 
United  States  and  according  to  Kel- 
logg extends  as  far  west  as  the  great 
plains.     It  also  occurs  in  California. 

Another  house-infesting  species  is 
the  native  American  cockroach,  Peri- 
planeta  americana  Linn.  (Fig.  36),  a 
light  chestnut-colored  species,  which  reaches  a  length  of  an  inch  and  a 
half  and  has  long  wings  in  both  sexes.  This  is  also  a  common  species 
in  the  middle  and  western  states,  being  especially  abundant  in  Mexico 
and  Central  America.  It  resembles  a  slightly  shorter  species  occupy- 
ing about  the  same  territory  in  the  United  States,  namely,  Periplaneta 
australasice  Fabr.  (Fig.  37),  which  differs  further  in  that  the  Austra- 
lian roach  has  a  yellowish  border  around  the  pronotum,  extending  partly 
down  the  outer  margins  of  the  wing  covers.  Our  commonest  native 
outdoor  species  is  Ischnoptera  perinsyhanica  De  G.  To  these  common 
forms  might  be  added  a  list  of  exotic  roaches  constantly  coming  to 
our  shores  on  shipboard  from  the  Orient  and  elsewhere,  but  which  have 
never  secured  a  foothold. 

Life  History  and  Habits  of  the  Croton  Bug.  —  The  croton  bug  is 


Fig.  36.  —  The  American  cockroach, 
Periplaneta  americana.      X  1.3. 


40 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


nocturnal  in  habit,  but  may  be  seen  roaming  about  during  the  day, 
although  its  activity  is  then  limited.  Generally  the  roaches  collect  in 
huddled  groups  during  the  day  and  remain  inactive.  Their  main 
requirements  for  activity  are,  first,  a  fairly  high  temperature ;  secondly, 
darkness;  and  lastly,  a  supply  of  food.  Roaches  are  commonly  en- 
countered in  kitchens,  galleys,  restaurants,  bakeries,  etc.  These  in- 
sects are  omnivorous,  favoring  starchy  and  sweet  materials ;  they  may 
also  feed  on  excrement  and  will  readily  devour  their  dead  brethren 
and  cast-off  skins. 

The  eggs  of  the  roach  are  laid  in  pairs  (13  pairs  usuall}-)  in  an  egg  case, 
or  oothecum  (Fig.  34),  which,  when  filled,  protrudes  from  the  abdomen 

of  the  female.  The  females  may  evi- 
dently carry  these  cases  about  with 
them  two  months  or  more,  when  they 
are  finally  deposited  in  some  dark 
crevice,  and  the  young  roaches  or 
nymphs  hatch  out  in  twelve  days  or 
less.  The  young  roaches  are  at  first 
almost  white  and  transparent,  but 
soon  become  brownish  and  resemble 
the  adults  except  for  size  and  absence 
of  wings.  The  young  roaches  molt 
soon  after  emergence  from  the  egg 
case  and  again  in  about  four  weeks. 
There  are  apparently  about  six  molts 
before  the  roaches  are  mature,  and 
Fig.  37. —  The  Australian  roach  Peri-     certainly  a  year  or  morc  is  required 

plajieta  australasice.       X  1.12.  ,      «  \  .     .  i-   i       i 

before  this  is  accomplished. 

Relation  to  Disease  Transmission.  —  Cockroaches  have  long  been 
looked  upon  with  some  suspicion  as  possible  carriers  of  disease  and  are 
certainly  regarded  with  much  disgust  by  everybody.  If  the  house  fly 
is  such  a  potent  transmitter  of  infection,  why  not  the  cockroach,  at  least 
to  a  large  degree  ?  While  the  house  fly  is  active  in  the  daytime,  walking 
over  prepared  human  food,  depositing  thereon  its  load  of  bacteria,  the 
cockroach  is  actively  engaged,  under  cover  of  night,  in  a  similar  per- 
formance. The  two  insects  by  analogy  must  relate  to  the  transmission 
of  bacteria  in  a  similar  manner,  i.e.  must  collect  bacteria  on  their  feet 
and  mouth  parts  by  crawling  and  feeding  on  filth  which  may  be 
charged  with  bacteria,  and  depositing  these  on  human  food,  while  in 
the  act  of  feeding. 

The  cockroach  has  biting  mouth  parts  like  the  grasshopper,  hence 
could  not  relate  to  the  transmission  of  disease  by  direct  inoculation,  as 
does  the  stable  fly,  for  example,  which  has  piercing  mouth  parts.  If 
the  structure  of  the  cockroach  is  such  that  it  can  pick  up  bacteria  easily, 
and  if  it  can  be  shown  that  the  cockroach  invades  places  where  infective 
material,  such  as  sputum  or  excrement,  is  found,  then  a  chain  of  strong 


COCKROACHES  — BEETLES  — THRIPS  41 

circumstantial  evidence  could  be  produced  that  the  roach  is  a  factor  in 
the  dissemination  of  such  diseases  as  tuberculosis,  dysentery,  cholera  and 
probably  typhoid  fever.  The  food  habits  of  the  roach  are  certainly  such 
that  there  is  ample  opportunity  for  the  contamination  of  the  food  of  man. 

Comparing  the  feet  and  mouth  parts  of  the  house  fly  and  the  croton 
bug,  it  will  be  seen  at  once  that  the  latter  is  far  less  adapted  to  the  col- 
lection of  filth,  inasmuch  as  the  feet,  especially,  are  not  so  well  provided 
with  spines  and  hairs  as  are  the  feet  of  the  house  fly.  However,  the 
weight  of  the  insect  and  surface  in  actual  contact  with  infective  mate- 
rial partly  compensates  for  the  above  structural  deficiency. 

Can  the  Roach  Pick  up  Specific  Bacteria  ?  —  In  order  to  answer 
this  question  one  of  these  insects  was  allowed  to  crawl  over  a  culture  of 
Bacillus  pyocyaneus  aureus,  a  green  chromogen,  in  a  test  tube.  The 
growth  on  the  agar  in  this  tube  was  not  very  profuse.  The  insect  was 
next  transferred  to  a  sterile  agar  plate  upon  which  it  was  permitted  to 
walk  one  minute.  The  roach  was  then  liberated  and  transferred  to  a 
second  plate  for  one  minute,  and  then  to  a  third  plate  in  a  similar  man- 
ner. The  agar  plates  were  then  incubated  for  24  hours  at  a  temper- 
ature of  37°  C.  At  the  end  of  this  time  a  good  growth  of  the  green 
chromogen.  Bacillus  pyocyaneus  aureus,  had  developed  on  all  three  plates. 

This  experiment  goes  to  prove  that  the  legs  of  the  roach  are  con- 
structed so  as  to  enable  it  to  pick  up  bacteria  of  a  given  kind  and  enough 
to  heavily  inoculate  at  least  three  plates. 

Can  the  Roach  Carry  Specific  Bacteria  to  Human  Food  ?  —  Having 
determined  that  the  roach  can  pick  up  known  bacteria,  the  next  thing 
was  to  prove  that  it  could  deposit  these  same  organisms  on  human  food. 
In  order  to  do  this  one  grain  of  sugar  was  exposed  to  a  cockroach  that 
had  previously  walked  across  an  agar  plate  culture  of  Bacillus  pyo- 
cyaneus aureus,  the  same  chromogen  used  above.  The  insect  remained 
with  the  sugar,  feeding  on  it,  for  three  minutes.  The  sugar  was  then 
dissolved  in  5  cc.  of  sterile  water  and  plated  on  three  agar  plates,  using 
1  cc.  of  the  solution  for  each.  The  plates  were  incubated  for  24  hours 
at  37°  C.  B.  pyocyaneus  aureus  was  recovered  on  all  three  plates,  the 
growth  on  none  being  scanty.  The  recovery  of  the  test  culture  in  the 
sugar  solution  showed  that  the  contaminated  cockroach  could  in  turn 
contaminate  the  food  over  which  it  crawled  and  upon  which  it  fed. 

The  Bacterial  Population  of  the  Croton  Bug.  —  Six  individuals  were 
selected  from  a  collection  of  roaches  taken  from  various  localities  and 
permitted  to  crawl  for  one  minute  over  six  sterile  agar  plates  (one  roach 
for  each  plate).  These  plates  were  incubated  for  48  hours  at  37°  C. 
Each  plate  showed  a  good  growth,  the  colonies  on  examination  proving 
to  be  saprophytic  without  exception. 

To  secure  an  approximate  estimate  of  the  number  and  kind  of  bac- 
teria carried  by  roaches,  two  of  these  insects  were  treated  as  follows. 
After  sterilizing  pipettes,  forceps,  tubes,  etc.,  5  cc.  of  distilled  water  was 
placed  in  each  of  the  five  test  tubes.     Into  these  tubes  were  placed  the 


42 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


legs  and  antennae  of  the  roaches,  —  the  posterior  pair  of  legs  of  one  roach 
into  one  tube,  those  of  the  other  roach  in  a  second  tube,  the  antennae 
of  both  roaches  in  a  third,  and  the  remaining  pairs  of  legs  of  the  first 
roach  in  the  fourth  and  the  remaining  pair  of  legs  of  the  other  roach  in  the 
fifth  tube.  The  stomach  contents  were  plated  on  agar.  The  tubes 
were  shaken  vigorously  for  three  minutes  in  order  to  wash  the  parts 
well  and  then  1  cc.  of  the  water  in  each  tube  was  plated  on  agar  and 
incubated  24  hours  at  37°  C.  The  results  were  all  positive,  as  the  fol- 
lowing table   (Table  I)   indicates : 

TABLE  I 

Showing  Number  and   Kind   of   Bacteria   Carried   on   Individuals   of 

THE  Croton  Bug 


No.  OP 

THE 

Roach 

Part  op  the 
Roach  Plated 

Bacterial 
Count  per  cc. 

Kind  of  Bacilli  Present 

1 

Posterior 
pair  of  legs 

1200+ 

(a)  Staphylococcus  alhus 

(b)  Non-sj)ore-bearing  bacillus 

2 

Posterior 
pair  of  legs 

1600+ 

(a)  Staphylococcus  alhus 

(6)  Non-spore-bearing  bacillus 

1 

Remaining 
legs 

950 

(a)  Staphylococcus  alhus 

(b)  Small  non-spore-bearing  bacillus 

(c)  Spore-bearing  air  bacillus 

2 

Remaining 
legs 

1200 

(a)  Spore-bearing  air  bacillus 
(6)  Staphylococcus  alhus 

1-2 

Antennae 

384 

(a)  Spore  bearing  air  bacillus 
(h)  Staphylococcus  aureus 
Yellow  pigment 

1 

Stomach 
contents 

14 

(a)  Minute  bacilli  (unidentified) 

Total 

5348+ 

for  a  dilution  of  ^ 

5  X  5348+  -r-  2  =  13,370+  bacteria,  —  minimum  number  present  on  each  roach 


From  the  above  table  it  will  be  seen  that  each  roach  carried  on  its 
feet  and  antennae  and  in  its  stomach  a  minimum  of  13,370  bacteria. 
While  this  does  not  represent  a  fair  estimate  for  all  roaches,  since  only 
two  individuals  were  used,  we  are  here  shown  that  the  roach  can  carry  a 
large  number  of  bacteria.  Esten  and  Mason  (Storrs  Agric.  Exp.  Sta., 
Bull.  No.  51)  have  shown  that  the  number  of  bacteria  carried  by  a  fly 
range  all  the  way  from  550  to  6,600,000,  with  an  average  of  one  and  one 
fourth  million  bacteria  on  each.  Thus  by  comparison  it  may  be  seen 
that  the  roach  probably  carries  fewer  bacteria. 


COCKROACHES  — BEETLES  — THRIPS  43 

It  is  furthennore  interesting  to  note  that  there  were  more  bacteria 
on  the  single  pair  of  posterior  legs  than  on  the  remaining  two  pairs  com- 
bined. This  is  probably  explained  by  the  use  the  cockroach  makes  of 
its  hinder  pair  of  legs.  The  tibipe  and  tarsi  are  in  contact  with  the  sur- 
face on  which  the  insect  walks,  being  parallel  with  the  body.  Very  often 
the  insect  stands  on  the  hind  pair  of  legs,  with  the  remaining  legs  barely 
touching  the  surface.  The  fore  legs  are  also  frequently  brushed  by  the 
antennae. 

Environmental.  —  The  last  link  in  the  chain  of  evidence  against  the 
cockroach  is  its  normal  environment,  which  gives  the  insect  an  oppor- 
tunity to  contaminate  itself  with  pathogenic  organisms,  if  present. 
Such  an  environment  would  be  an  accessible  insanitary  privy,  close  to 
the  kitchen  or  pantry,  in  which  case  there  is  at  least  the  possibility  of 
the  transference  to  the  food  of  man  of  one  of  the  causative  organisms 
(bacillary)  of  dysentery,  diarrhea  and  cholera  and  still  more  remotely 
of  typhoid  fever. 

Conditions  favoring  the  transmission  of  the  tuberculosis  bacillus 
are  relatively  more  common.  Two  instances  may  be  cited.  These 
existed  in  the  forecastle  of  two  vessels.  On  these  two  vessels  no  sepa- 
rate mess  rooms  were  provided  for  the  sailors,  their  food  being  served 
in  the  same  room  in  wiiich  they  slept.  Bread,  butter  and  sugar  were 
usually  left  uncovered  on  the  table,  readily  accessible  to  cockroaches, 
which  swarmed  over  floors  and  walls.  Sailors  occupying  the  rooms  were 
in  the  practice  of  constantly  spitting  on  the  floor.  If  one  or  more  of 
these  sailors  should  be  tubercular,  there  is  at  least  the  possibility  of  germ 
transmission  by  the  roach  to  the  food.  A  third  instance  may  be  men- 
tioned, that  of  a  certain  roach-infested  residence  occupied  by  a  con- 
sumptive in  the  last  stages  of  the  disease.  This  patient  did  not  use 
sputum  cups,  and  although  belonging  to  a  refined  family  had  the  per- 
nicious habit  of  spitting  in  the  darker  corners  of  the  room  and  behind 
pieces  of  furniture.  In  this  house  lived  a  half  dozen  students  who  also 
took  their  meals  there.  Roaches  were  commonly  seen  in  the  room  in 
which  the  patient  lived  and  roaches  swarmed  in  the  pantry  and  kitchen 
at  night.  Surely  here  existed  a  condition  that  favored  the  transmission 
of  tubercle  bacilli.  Unfortunately  the  reputation  of  this  house  in  one 
of  the  more  select  districts  of  the  city  was  of  more  importance  than 
the  lives  of  the  inmates  of  the  house. 

Other  Considerations.  —  The  fact  that  roaches  also  feed  on  fecal 
matter  may  lead  to  further  complications,  which,  owing  to  lack  of 
experimental  evidence,  cannot  be  considered  here  further.  However, 
it  was  very  early  known  that  cockroaches  may  become  infected  with 
Filaria  rytvpleu rites  Delonchamps  of  the  rat,  by  feeding  on  rat  feces, 
and  that  other  rats  may  become  infected  in  turn  by  feeding  upon  such 
roaches.  Galeb  in  Comprend  Rendu  (1878)  reports  his  observations 
upon  the  transmission  of  this  nematode.  He  discovered  numerous 
parasites  in  the  "  adipose  tissue  "  of  the  roach  Blatta  orientalis,  which 


44  MEDICAL  AND   VETERINARY  ENTOMOLOGY 

were  found  to  be  identical  with  nematodes  found  in  the  rat,  Mus  de- 
cumanus.  He  also  found  hair  of  the  rat  in  the  alimentary  canal  of  the 
roach.  On  feeding  rats  {Mus  rattus)  with  infected  roaches  and  examin- 
ing them  after  the  expiration  of  eight  days,  he  found  the  parasites  in  the 
folds  of  the  mucous  membrane  of  the  stomach.  Several  nematodes 
(three  females  and  one  male)  had  already  developed  sexual  organs. 
More  recent  experimental  evidence  indicates  that  the  roach  is  almost 
certainly  the  intermediary  host  of  this  nematode. 

Control.  —  Numerous  methods  have  been  evolved  to  combat  the 
cockroach,  and  it  is  quite  certain  that  this  insect  can  be  controlled  in 
dwellings,  restaurants  and  the  like.  One  method  which  has  been  found 
useful  for  the  larger  less  abundant  form  is  the  trap.  This  consists  of  a 
deep,  smooth-walled  vessel  (fruit  jar  or  the  like)  into  which  is  placed  a 
favorite  roach  food,  such  as  chocolate,  or  molasses  (stale  beer  or  ale  are 
also  recommended) .  Sticks  leading  to  the  top  of  the  jar  must  be  provided 
in  order  that  the  roaches  can  easily  reach  the  mouth,  and  in  their  en- 
deavor to  get  at  the  food  tumble  into  the  trap.  If  there  is  a  liquid  in 
the  trap,  the  roaches  are  drowned;  otherwise  they  must  be  killed  by 
scalding. 

Trapping  methods  are  least  successful  in  the  control  of  the  croton 
bug;  it  is  certainly  far  more  wary  than  the  larger  species.  The  ordi- 
nary glass-jar-trap  method  employed  for  the  larger  species  is  not  effec- 
tive. The  croton  bug  can  crawl  up  the  sides  of  a  glass  jar  without  diffi- 
culty and  thus  make  its  escape.  A  dark  box  trap  is  preferable  with  one 
or  more  tubular  pasteboard  entrances  projecting  both  inside  and  out- 
side. The  mouth  of  the  tube  inside  the  box  must  be  guarded  either  with 
a  single  trap  door  or  adhesive  substance  around  the  outside  of  the  tube 
and  immediately  adjacent  to  the  mouth  to  prevent  the  roaches  from 
escaping  after  feeding  on  the  bait.  The  box  may  be  baited  with  sugar, 
sweet  chocolate,  a  little  stale  beer  or  the  like.  After  the  roaches  have 
been  captured  they  are  shaken  out  through  a  lid  into  kerosene  or 
hot  water.  The  box  is  then  once  more  baited  and  placed  in  posi- 
tion. 

]\Iore  satisfactory  results  are  obtained  by  means  of  poisons.  When 
the  word  poison  is  used  in  this  connection  it  does  not  necessarily  imply 
that  it  is  a  poison  also  to  human  beings,  since  there  are  some  materials 
which  act  in  this  way  when  eaten  by  insects  but  are  non-poisonous  to 
human  beings,  except,  of  course,  when  taken  in  large  quantities ;  among 
such  materials  are  borax  and  formalin.  Borax  is  frequently  used  as  an 
ingredient  in  the  preparation  of  roach  and  ant  poisons.  Thus  equal 
parts  of  chocolate,  or  powdered  sugar,  and  borax  well  mixed  (this  is 
important)  provide  an  excellent  roach  powder.  This  powder  should 
be  placed  in  little  heaps  or  in  windrows  easily  accessible,  or  may  be 
sprinkled  in  the  crevices  whence  the  insects  come.  Persian  insect 
powder  or  pyrethrum  stupefies  the  insects.  Dusting  the  haunts  of  the 
roach  liberally  with  flowers  of  sulphur  also  proves  effective  as  a  re- 


COCKROACHES  — BEETLES  — THRIPS  45 

pellent.  Two  methods  mentioned  by  F'elt  ^  are  the  following :  "  The 
smoke  of  burning  gunpowder  is  very  obnoxious  and  deadly  to  roaches, 
particularly  the  English  roach.  The  moistened  powder  should  be 
molded  into  cones,  placed  in  an  empty  fire-place  and  ignited.  It  is 
particularly  valuable  in  the  case  of  old  houses."  A  second  method, 
viz. :  "  A  relatively  simple  method,  described  by  Mr.  Tepper  of 
Australia,  is  to  mix  plaster  of  paris,  one  part,  and  flour  three  or  four 
parts,  in  a  saucer  and  place  the  preparation  about  the  haunts  of  the 
pests.  Near  by  there  should  be  a  saucer  containing  a  little  water  and 
made  easily  accessible  to  the  roaches,  laying  a  few  sticks  as  bridges  up  to 
the  rim.  The  insects  eat  the  mixture,  drink  the  water  and  soon  succumb." 
Fumigation  with  hydrocyanic  acid  gas,  carbon  bisulphid  or  sulphur 
may  be  resorted  to  with  much  success ;  however,  should  not  be  under- 
taken without  experienced  assistance,  since  the  behavior  of  these  gases 
must  be  fully  understood.  » 


B.   The  Beetles 
Order  Coleoptera 

The  beetles  may  easily  be  distinguished  from  other  insects  by  the 
following  characters :  the  mouth  parts  are  of  the  biting  type,  mandi- 
bles strongly  developed ;  two  pairs  of  wings  are  present  of  which  the  for- 
ward pair  is  hardened  and  does  not  overlap  at  the  tip ;  the  ventral  por- 
tion of  the  abdominal  segments  consists  of  chitinous  plates  extending  at 
least  halfway  round  the  body.  (In  other  insects  these  ventral  plates 
are  much  shorter  as  a  rule.) 

The  metamorphosis  of  Coleoptera  is  complex  (egg,  larva,  pupa, 
imago)  with  the  occurrence  of  hypermetamorphosis  in  a  number  of 
species.  The  larvae  of  this  order  are  commonly  called  "  grubs  "  and 
may  be  recognized  by  the  presence  of  three  pairs  of  rather  feeble  legs. 

Only  a  few  families  of  this  great  order  of  insects  concern  us,  and  only 
those  which  by  habit  come  in  contact  with  diseased  animal  carcasses, 
or  attack  other  living  animals  or  which  possess  medicinal  properties. 

Scavenger  Beetles.  —  All  the  scavenger  beetles  are  of  interest  in 
this  connection  since  the  habit  of  feeding  on  dead  animal  matter 
might  accidentally  bring  them  in  contact  with  the  infection.  Infec- 
tion may  be  carried  in  two  ways,  namely,  first  mechanically  on  the 
body,  legs  or  mouth  parts,  or  secondly,  in  the  excreta.  The  latter 
method  involves  attenuation  in  that  the  pathogenic  organism  may 
become  reduced  in  virulence  in  its  passage  through  the  alimentary  canal 
of  the  insect. 

Among  the  families  of  scavenger  beetles  are  the  Staphylinidse  or  rove 
beetles  (not  all  animal  feeding),  recognized  by  the  abbreviated  condition 

1  Felt,  Ephraim  Porter,  1909.  Control  of  Household  Insects.  New  York 
State  Museum,  Bulletin  No.  129  (Albany). 


46 


MEDICAL  AND   VETERINARY   ENTOMOLOGY 


Fig.  38.  —  Rove    beetles    (Staphylinidse). 
a.  Creophilus  ;    h.   Staphylinus.       X  1.5. 


of  the  wing  covers  (elytra),  thus  exposing  the  abdomen  dorsally,  and 
giving  these  beetles  a  larval  or  worklike  appearance,  augmented  by  the 
flexibility  of  these  parts.  The  functional  wings  are  folded  up  and  con- 
cealed under  the  elytra.  The  range  in  size  in  this  family  is  enormous. 
One  very  small  species  in  the  act  of  swarming  is  known  to  get  into  the 
eyes  of  people  when  driving,  cycling  or  motoring,  causing  a  severe  burn- 
ing sensation  by  means  of  the  vile- 
smelling  body  secretions.  The  spe- 
cies commonly  met  with  on  turning 
over  carcasses,  hides,  heaps  of  bones 
and  other  animal  rubbish,  belong 
to  two  genera ;  namely,  Creophilus 
(Fig.  38  left)  and  Staphylinus  (Fig. 
38  right),  which  include  species 
ranging  from  one  half  to  one  inch 
in  length.  A  second  family  to  be 
considered  are  the  Silphidae,  or 
sexton  beetles,  also  known  as  car- 
rion beetles.  In  habit  these  insects 
are  more  decidedly  scavenger  than 
the  preceding,  feeding  almost  ex- 
clusively on  dead  flesh,  both  as  larvae  and  adults.  Again  two  genera 
will  serve  to  illustrate  the  commoner  forms,  namely,  Silpha  (Fig.  39 
left)  and  Necrophorus  (Fig.  39  right).  These  two  genera  are  well  illus- 
trated as  to  relative  size  and  general  shape  by  the  accompanying  figures. 
A  third  family,  the  Histeridse,  is  composed  of  a  group  of  small- 
sized,  short,  shining,  black  beetles  commonly  found  about  decompos- 
ing animal  matter. 

The  fourth  family,  Derm- 
estidse,  also  includes  only  small 
forms,  about  one  third  of  an 
inch  and  less  in  length.  In 
shape  they  are  elliptical,  usu- 
ally dark  grayish  or  brownish 
in  color.  Skins  and  other  ani- 
mal specimens  in  museums  are 
often  ruined  by  the  museum 
pest,  Anthrenus  museorum. 
Linn,  or  Anthrenus  verbasci 
Linn.,  if  proper  precautions  are 
not  taken.  This  damage  is  practically  all  done  by  the  larvae,  as  is  the 
case  with  the  larder  beetle,  Dermestes  lardarius  Linn,  and  D.  vulpinus 
Fabr.  and  the  carpet  beetle,  Anthrenus  scrophularicB  Linn. 

Relation  to  Disease.  —  Where  hides  taken  from  anthracic  animals 
or  the  carcasses  are  attacked  by  scavenger  insects  it  is  more  than  likely 
that  there  will  be  danger  from  this  source.     The  following  statements 


Fig.   39. — Sexton   t)eetles    (Silphidte).     a.  Sil- 
pha atnericana;    b.   Necrophorus  sp.     X  1.5. 


COCKROACHES  —  BEETLES  —  THRIPS 


47 


taken  from  Niittall  ^  bear  directly  on  this  subject,  viz.  "  Proust  (1894), 
in  examining  goatskins  taken  from  anthracic  animals,  found  quantities 
of  living  Dermestes  vulpinus  upon  them.  He  found  virulent  anthrax 
bacilli  in  their  excrements,  as  also  in  the  eggs  and  in  the  larvae.  It  is 
evident  from  this  that  these  insects  which  feed  on  the  skins  permit  the 
anthrax  spores  to  pass  uninjured  through  their  alimentary  tract.  Heim 
(1894)  also  had  occasion  to  examine  some  skins  which  were  suspected 
of  having  caused  anthrax  in  three  persons  engaged  in  handling  the 
leather.  He  found  larvse  of  Attagenus  pellio  Linn.,  Anthrenus  museoruvi 
Linn,  (both  Dermestidae)  and 
Ptinus,  also  fully  developed 
insects  of  the  latter  species 
on  the  skins.  All  these  in- 
sects had  virulent  anthrax 
bacilli  (spores)  on  their  sur- 
face and  in  their  excreta, 
from  which  Heim  concludes 
they  might  spread  disease. 
He  says  the  excreta  are  very 
light  and  easily  scattered  by 
the  slightest  current  of  air. 
Heim  does  not  believe  the 
bacilli  multiply  in  the  bodies 
of  these  insects,  but  that 
the  latter  may  be  dangerous 
through  their  scattering  the 
spores  about." 

May  Beetles  and  Thorn- 
headed  Worms. — ^May  beetles 
or  cockchafers  (Family  Scara- 
baeidae)  are  known  to  be  in- 
termediary hosts  both  in  the 
larval  and  adult  stages  of  the 
thorn-headed  worm  (Fig.  40),  Echinorhynchus  gigas  Goeze,  a  parasite  of 
swine  also  said  to  occur  in  man  in  rare  cases.  This  nematode  worm  in 
its  adult  stage  measures  from  20  to  30  cm.  in  length  and  about  3  to  5  mm. 
in  thickness,  and  inhabits  the  small  intestine  of  its  host.  The  eggs  are 
deposited  in  this  habitat  and  pass  out  w^ith  the  feces  which  may  be  swal- 
lowed by  the  larvae  of  the  cockchafers.  These  are  often  extremely  abun- 
dant among  the  rootlets  of  grass  in  heavily  sodded  pastures,  and  swine 
with  free  range  are  exceedingly  fond  of  these  grubs,  in  search  of  which 
they  diligently  root  up  the  soil  with  their  snouts.  Thus  every  oppor- 
tunity is  given  for  the  grubs  to  become  infected  and  in  turn  the  swine. 

1  Nuttall,  George  H.  F.  On  the  Role  of  Insects,  Arachnids  and  Myriapods, 
as  Carriers  in  the  Spread  of  Bacterial  and  Parasitic  Diseases  of  Man  and  Animals. 
Johns  Hopkins  Hospital  Reports,  Vol.  VIII,  Nos.  1-2,  1899. 


Fig.  40.  —  Thorn-headed  worm,  Echinorhynchus 
gigas,  of  swine,  requiring  a  May  beetle  (Lach- 
nosterna  or  Melolontha)  as  intermediary  host. 
X  1. 


48 


MEDICAL  AND   VETERINARY   ENTOMOLOGY 


Fig.  41 


May     beetles    or    cockchafers,     Cotalpa 
(left)    and    Lachnosterna   fusca    (right). 

Serve  as  intermediary  hosts  for  the  thorn-headed 

worm  of  swine.       X  1.2. 


After  the  ova  have  been  ingested  the  larvae  hatch  in  a  few  days 

within  the  intestine  of  the 
insect  and  proceed  to 
burrow  through  the  in- 
testinal wall  and  into  the 
muscles,  where  they  are 
said  to  encyst  them- 
selves. In  Europe  the 
intermediary  host  is  com- 
monly Melolontha  melolon- 
tha  Linn,  (vulgaris  Fab.) 
and  Cetonia  aurata  Linn. 
]\Iay  beetles  of  the  genus 
Lachnosterna  (Fig.  41) 
(according  to  Stiles,  Lach- 
nosterna arcuata  Smith  and 
others)  are  probably  all 
more  or  less  concerned. 
The  life  history  of  nearly 
all  May  beetles  is  quite 

long,  the  larval  stage  alone  often  requiring  nearly  .three  years. 
In  districts    infested  with    the   thorn-headed  worm  a    systematic 

crusade    against    cockchafers 

would  be  the  logical  means  of 

control,     together    with    the 

treatment  of  swine  with  vermi- 
fuges, the  swine  being  properly 

coralled  so  that  the  feces  can 

be  disinfected  with  formalin  or 

other  effective  disinfectant. 
Saw-toothed  Grain  Beetle. 

—  At  least  one  case  has  been 

reported  to  the  writer  in  which 

the  saw-toothed  grain  beetle, 

Silvanus    surinamensis    Linn. 

(Fig.  42),  of  the  family  Cucu- 

jidae,   invaded   sleeping   quar- 
ters, causing  great  annoyance 

to  the  occupants  by  nibbling 

at  and  crawling  about  on  the 

body.    The  infestation,  which 

lasted  several  days,  was  traced 

to  the  bathroom,  thence  out 

of  the  house  through  the  yard    Fi«-  42 

and  into  an  old  barn  under  the 

stalls,  where  unquestionably  grain  from  the  manger  had  accumulated 


The  saw-toothed  grain  beetle,  Silvanus 
surinamensis.       X  33. 


COCKROACHES  — BEETLES  — THRIPS  49 

and  where  these  beetles  had  been  bred  in  great  numbers.  The  dry 
California  summer  had  pretty  surely  driven  these  insects  to  the  bath- 
room for  water,  and  the  attack  upon  the  occupants  of  the  adjoining 
bedchamber  was  merely  an  incidental  matter.  However,  it  is  interest- 
ing to  note  that  an  instance  is  recorded  in  Braun's  Parasites  of 
Man,  viz.  "  Taschenberg  records  this  beetle  as  having  invaded  some 
sleeping  apartments  adjoining  a  brewery  where  stores  were  kept,  and 
annoying  the  sleepers  at  night  by  nipping  them  in  their  beds." 

Cantharidin,  Spanish  Fly.  —  Although  a  few  other  insects  secrete 
vesicating  fluids,  the  principal  source  for  medicinal  purposes  is  the  group 
of  insects  known  as  the  blister  beetles  (Meloidse)  of  which  the  Spanish 
fly,  Lytta  vesicatoria  Linn.  (Fig.  43),  is  the  most  important  member. 


Fig.  43.  —  The  Spanish  fly,  Lytta  vesicatoria.     a.  female  ;   h.  male.       X  2.1. 

This  beetle  is  a  European  form  found  most  abundantly  during  a  cer- 
tain season  of  the  year  in  Spain,  Southern  France  and  even  at  times  in 
Germany;  Petrograd  supplies  also  a  large  quantity  of  superior  can- 
tharidin. The  Spanish  fly  possesses  a  fine  golden  green  or  bluish  color, 
ranges  from  |^  to  |  of  an  inch  in  length  and  makes  its  appearance  quite 
suddenly  in  early  summer,  when  it  may  be  collected  by  the  hundreds, 
clinging  principally  to  such  vegetation  as  the  ash,  privet  and  lilac. 
The  peculiar  hypermetamorphosis  of  these  insects  and  their  larval  habits 
give  to  them  some  obscurity  during  their  early  development  and  the 
sudden  appearance  and  equally  sudden  disappearance,  owing  to  short 
adult  life,  lent  the  belief  that  they  were  migrating  forms. 

The  collection  and  preparation  of  the  beetles  provides  an  occupation 
for  many  persons  during  the  brief  period.  This  process  also  requires 
special  precautions  owing  to  the  vesicating  properties  of  the  insects. 


50         MEDICAL  AND   VETERINARY  ENTOMOLOGY 

The  best  quality  of  cantharidin  produced  from  the  pulverized  beetles  is 
the  result  of  special  care  in  the  drying,  which  must  be  gradual.  Of 
cantharidin,  SoUman  ^  (p.  705)  says  it  is  the  most  important  local  irri- 
tant. "  It  is  a  crystalline  principle,  the  anhydrid  of  cantharidic  acid. 
It  combines  readily  with  alkalines,  forming  soluble  salts  ...  it  was 
isolated  by  Robiquet  in  1812  from  the  Spanish  fly  .  .  .  Lytta  vesica- 
toria.  .  .  .  Cantharidin  is  readily  absorbed  from  all  surfaces.  Even 
when  applied  to  the  skin,  sufficient  may  be  absorbed  to  irritate  the  kid- 
neys, so  that  fly  blisters  are  contraindicated  in  nephritis.  It  is  excreted 
mainly  by  the  kidneys.  It  irritates  the  gastro-intestinal  tract  even 
when  injected  hypodermically  so  that  some  must  be  excreted  by  this 
channel.  .  .  .  Cantharidin  penetrates  the  epidermis  quite  readily 
and  produces  violent  but  superficial  irritation.  This  results  in  vesica- 
tion. Very  small  quantities  suffice  for  this  purpose,  jq  mg.  cantharidin 
.  .  .  will  produce  blisters  on  the  human  skin  in  the  course  of  a  few 
hours." 

As  to  therapeutic  uses  the  same  author  states  :  "  Cantharis  is  the  most 
useful  of  vesicants.  .  .  .  The  vesicant  action  of  cantharides  develops 
rather  slowly.  (It)  is  one  of  the  most  useful  remedies  in  the  treatment 
of  baldness.  It  is  used  in  the  form  of  tincture,  very  greatly  diluted  with 
alcohol.  For  treatment  of  impotence  Cantharis  is  one  of  the  most 
certain,  acting  through  reflex  irritation  from  the  urethral  mucous 
membrane.  It  is,  however,  quite  dangerous,  since  effective  doses  are  apt 
to  set  up  considerable  nephritis." 

C.    Thrips 
Order  Physopoda 

Thrips  and  Sneezing.  —  The  introduction  of  foreign  particles  into 
the  nostrils  causes  sneezing,  this  phenomenon  being  easily  induced  by 
irritation  of  the  mucous  membrane  of  the  nasal  chambers.  Such  a 
paroxysm  often  follows  when  a  flower  is  held  close  to  the  nose  and  a 
strong  inhalation  is  made  to  receive  the  odor.  This  strong  inhalation 
frequently  brings  with  it  small  insects  which  were  crawling  about  on 
the  petals  of  the  blossom.  Insects  habitually  inhabiting  blossoms  are 
most  likely  to  be  the  guilty  ones  and  of  these  the  commonest  minute 
forms  are  members  of  the  order  Physopoda  (Thysanoptera)  commonly 
called  thrips. 

Characteristics.  —  These  rather  active  insects  are  characterized  by 
their  small  size  (1  to  2  mm.)  together  with  the  following  unique  struc- 
tures, viz. :  the  foot  terminates  in  a  bladder-like  organ,  whence  the 
term  Physopoda ;  the  wings  are  narrow,  but  this  narrowness  is  com- 
pensated for  by  a  great  development  of  long,  closely  set  fine  hairs  along 
the  margins  of  each  wing,  whence  the  name  Thysanoptera    (bristle 

1  SoUman,  Torald,  1908.  Textbook  of  Pharmacology,  1070  pp.  W.  B. 
Saunders  Co. 


COCKROACHES  —  BEETLES  —  THRIPS 


51 


wings)  (Fig.  44a).     The  mouth  parts  are  also  distinctive  as  already 
explained. 

Systematic.  —  The  order  is  divided  into  two  subdivisions  based  on 
the  form  of   ovipositor,  —  tubular  in  Tubulifera  (Fig.  446) ;    saw-like 

in    Terebrantia     (Fig. 

44c).  In  the  former 
subdivision  the  ovi- 
positor is  cylindrical, 
telescoping  in  the  last 
segment  of  the  abdo- 
men and  ending  in  a 
circlet  of  bristles ;  the 
following  commoner 
forms  are  representa- 
tives of  this  division : 
Phleothrips  verbasci, 
mullein  thrips ;  Phleo- 
thrips nigra,  clover 
thrips,  black  in  adult 
but  bright  red  in  the 
larval  stage.  The  sec- 
ond subdivision,  Tere- 
brantia, is  represented 
by  Euthrips  tritici 
Fitch.,  orange-yellow  in  color,  and  found  in  many  blossoms  according 
to  the  time  of  blossoming  (apple  blossoms,  strawberry  blossoms,  citrus 
blossoms,  and  grasses) ;  Euthrips  striatus  Osb.  is  the  grass  thrips,  also 
yellow,  but  smaller  than  Eii.  tritici  Fitch.  ;  Euthrips  pyri  Dan.  is  the 
pear  thrips  of  the  Santa  Clara  Valley  and  elsewhere. 


Fig.  44.  —  Thrips,  Order  Physopoda.  (a)  Shows  charac- 
teristic bhidder  feet  and  bristle  wings.  X  28.  (b) 
Tubular  ovipositor  of  Tubulifera.  (c)  Saw-like  ovi- 
positor of  Terebrantia. 


CHAPTER  VII 


THE  LICE 


A.   The  Biting  Lice 

Order  Mallophaga 

Characterization.  —  This  group  of  parasites  is  not  easily  distinguish- 
able from  the  true  sucking  lice  (the  Pediculi)  which  they  closely  resemble 
in  habit  and  general  form.  In  mouth  parts  they  are,  however,  very 
different ;  the  former  are  provided  with  mandibles  used  in  feeding,  while 
the  latter  have  a  long  protrusible  sucking  proboscis.  Furthermore,  the 
sucking  lice  are  restricted,  as  far  as  known,  to  mammals,  while  the 
biting  lice  inhabit  both  mammals  and  birds.  The  common  name 
"  bird  lice  "  often  applied  to  these  insects  is  misleading  for  this  reason. 
As  in  the  sucking  lice  each  species  is  usually  restricted  to  a  specific  host. 
The  body  is  compressed  dorsoventrally,  an  aid  to  easy  locomotion 

among  the  hairs  or  feathers  of 
the  host.  Wings  are  entirely 
absent,  there  being  no  trace  of 
these  organs  present.  The  sharp 
mandibles  are  situated  in  most  of 
the  species  on  the  ventral  surface 
of  the  head,  somewdiat  posterior 
to  the  tip,  and  may  be  seen  under 
the  microscope  as  conspicuous 
black-tipped  objects. 

Habits  and  Life  History.  — 
The  biting  lice  deposit  their  eggs 
on  the  hairs  or  feathers  of  the 
host  (Fig.  45),  to  which  they  are 
securely  attached  by  means  of  a 
gluey  secretion.  After  five  to 
eight  days  incubation  the  young 
lice  emerge  and  begin  their  active 
life  on  the  host,  which  they  do 
not  leave  as  a  rule  except  to  crawl 
off  on  to  another  individual  of  the  same  species,  ordinarily  when  in 
close  contact.  Under  severely  infested  conditions  among  poultry  there 
may  possibly  be  a  migration  from  the  host  to  the  roosts  and  even  to 

52 


Fig.  45.  —  Eggs  of  biting  lice  (Mallophaga) 
on  feathers  of  a  bird.     (Much  enlarged.) 


THE   LICE 


53 


Fig.  46.  —  The  biting  dog 
louse,  Trichodectes  latus. 
X35. 


other  animals,  but  the  writer's  experience  has 

been  that  these  infestations  are  generally  due  to 

poultry  mites  which  often  infest  every  nook  and 

crevice  of  the  henhouse.     The  biting  lice  are  so 

well  adapted  to  their  habitat  that  they  cannot 

well  exist   away  from  the  host  for  more  than 

several  hours.     Their  food  consists  of  exudations 

from  the  skin,  epidermal  scales,  bits  of  feathers 

and  hair.     INIaturity  is  ordinarily  reached  in  from 

three  to  four  weeks,  during  which  time  there  are 

apparently  about  four  or  five  molts,  with   no 

conspicuous  change  in  form. 

Damage  Done.  —  The  damage  done  by  the 

biting  lice  is  largely  restricted  to  poultry,  al- 
though some  trouble  may 
ensue  when  mammals  are 

badly  infested.  The  trouble  is  largely  that  of 
irritation  due  to  the  crawling  about  and  gnaw- 
ing habits  of  the  parasites.  This  irritation 
causes  the  host  to  become  restless,  thereby 
affecting  its  feeding  habits  and  proper  diges- 
tion, producing  weakness  and  susceptibility  to 
disease.  A  "  lousy  "  flock  of  chickens  is  not  a 
profitable  investment. 

Systematic.  —  The  biting  lice  (Mallophaga), 
of  which  there  are  over  a  thousand  species,  may 
be  grouped  into  two  suborders  based  on  the 
following  characters,  —  conspicuous  antennae, 
3  or  5  segmented,  palpi 
absent,  rather  sluggish  in 
habit,  —  suborder  Ischno- 

cera;    or,   concealed    four-segmented    antennge, 

palpi  present,  active  in  habit,  —  suborder  Am- 

blycera. 

The  suborder  Ischnocera  is  subdivided  into 

two  families,  viz. :    Trichodectidse,   species  .  in- 
festing mammals, — ^ antennae   three-segmented; 

Philopteridse,  inhabiting  birds  only, — ^  five-seg- 
mented antennae.     The  suborder  x\mblycera  is 

also    subdivided    into    two    families,    viz.    Gy- 

ropidse,  inhabiting  mammals  only ;  and  Liothe- 

idse,  inhabiting  birds  only.     The  families  may 

be  distinguished  by  the  tarsal  claws,  which  are 

distinctly  two  in  number  in  the  latter  case  and 

modified  into  clasping  organs  in  the  former,  one    Fig.  48.  —  Biting  louse  of 

£  ,^         ^  I     •  ^  ^  the  Angora  goat,  1  richo- 

01  the  claws  bemg  reduced.  dectes  hermsi.    x  22. 


Fig.  47.  —  The  biting  ox 
louse,  Trichodectes  scala- 
ris.    X  26. 


54 


MEDICAL  AND  VETERINARY   ENTOMOLOGY 


Species  of  Trichodectidae. — Only  a  few  of  the  commoner  species 
need   be  considered   here.     The  species  belonging  to  this  family  are 

all  small  in  size 
and  belong  to  the 
genus  Trichodectes. 
Trichodedes  latus 
Xitzsch  (Fig.  46)  is 
the  biting  louse  of 
the  dog,  most  nu- 
merous on  puppies. 
It  is  a  broad  short 
species  about  1  mm. 
long,  and  more  than 
half  as  wide.  Tri- 
chodectes suhrostratus 
Nitzsch  of  the  cat 
is  about  the  same 
length  as  T.  latus,  is 
not  so  broad  and 
has  a  longer,  more 
pointed  head.  Tri- 
chodectes scalaris 
Nitzsch  infests 
cattle.  The  distinct 
ladder-like  markings 
male,  (Fig.  47)  of  the 
abdomen      (present 


Fig.  49.  —  A  biting  louse  of  deer,  Trichodectes  tibialis 
left;    female,  right.      X  31. 


also  in  a  few  other  species  though  less  pronounced)   gives  rise  to  the 

specific  name.  -  Tiichodectes  paruminlosus  Piaget  is  one  of  the  biting 

lice  of  the  horse,  mule  and  ass.     Osborn^  describes 

this  form,  viz. :  "  the  head  is  decidedly  rounded 

in  front,  the  antennae  inserted  well  back,  so  that 

the  head  forms  a  full  semicircle  in  front  of  the  base 

of  the  antennse.     The  abdomen  is  more   slender 

and  tapering  than  in  scalaris.  .  .  .     The  color  is 

much  as  in  the  allied  species,  the  head,  thorax  and 

legs  being  a  bright  reddish  brown,  or  chestnut,  and 

the  abdomen  of  a  dusky  yellowish  color,  with  about 

eight  transverse  dusky  bands  occupying  the  central 

or  anterior  portions  of  the  segments  and  extending 

from  the  middle  line  a  little  more  than  halfway  to 

the  margin.     They  are  hardly  as  conspicuous  as  in 

scalaris."      Trichodectes    climax   Nitzsch    is    fairly 

common    on    goats,     Trichodectes    hermsi    Kellogg 

^  Osborn,  Herbert,  1896.     Insects  Affecting  Domestic  Animals.  •  U.  S.  Dept. 
of  Agr.,  Division  of  Entomology,  Bull.  No.  5,  N.S.     302  pp. 


Fig.  50. — A  hen  louse, 
Goniocotes  ahdomina- 
li>i.      X  10. 


THE  LICE 


55 


Fig.  51 .  —  A  turkey  louse, 
Goniodes  stylifer.     X  14. 


(Fig.  48)  is  abundant  on  the  Angora  goat,  and 
Trichodedes  tibialis  Piaget  (Fig.  49)  is  exceed- 
ingly abundant  on  deer. 

Species  of  Philopteridae.  —  Infesting  chickens 
the  following  members  of  this  family  may  be 
considered  :    Goniocotes  hologaster  Nitzsch,  about 

1  mm.  in  length,  has  a  squarish  head  with  angu- 
lated  temples ;  Goniocotes  abdominalis  Piaget 
(Fig.  50),  about  3  mm.  long,  broad  with  head 
circular  in  front ;    Lipeurus   variabilis  Nitzsch, 

2  mm.  in  length,  a  long,  very  slender  whitish 
species.  The  margins  of  the 
body  are  black ;  the  head  is 
large,  rounded,  and  the 
whole  appearance  sufficiently 
distinct  from  any  other 
species  infesting  the  chicken, 
so    that    there    can    be    no 

difficulty  in  distinguishing  it  at  a  glance.  Lipeurus 
heterographus  Nitzsch  is  said  to  differ  from  the 
above  in  having  the  "  head  rather  narrowed  in 
front  instead  of  inflated,  and  the  body  is  much 
stouter."  This  species  has  been  taken  by  Osborn 
from  chickens  at  Ames,  Iowa. 

Turkeys  are  commonly  infested  with  the  large 
(3  mm.  long)  Goniodes  stylifer 
Nitzsch  (Fig.  51),  which  has  the 
posterior  angles  of  the  head  ex- 
tended backward  into  long  pro- 
jections or  stylets  terminating 
in  bristles.  x4nother  louse  found 
on  turkeys  is  Lipeurus  polytra- 
pezius  Nitzsch,  like  all  members 
of  this  species,  long  and  slender, 
3  to  3^  mm. 

Ducks   and    geese    harbor    a 
rather     small-sized     species     of 

louse,  Docophorus  icterodes  Nitzsch  (1  mm.),  "with 

head    curiously   expanded    and    rounded    in    front, 

darkish  red  head  and  thorax  with  darker  bands,  and 

a  white  region  in  the  middle  of  the  abdomen."  — 

Kellogg.^     Another  common  species  infesting  ducks 

and  geese  is  Lipeurus  squalidus  Nitzsch  (Fig.  52), 

which,  according  to  Osborn,  "  is  about  4  mm.   in 

1  Kellogg,  Vernon  L.,  1905.     American  Insects,     vii  +  674  pp.     Henry  Holt 
&  Company. 


Fig.  52. — A  duck  louse, 
Lipeurus  squalidus. 
(Redrawn  after  Os- 
born.)      X  19. 


Fig 


53.  —  A  biting 
louse  of  the  guinea 
pig,  Gyropus  graci- 
lis. (Redrawn  after 
Osborn.)      X  35. 


56 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


length,  elongate  in  form,  and  of  a  light  yellowish  color,  with  dark  border 
to  the  head,  thorax  and  abdomen.  On  the  latter  this  border  is  broken 
into  a  series  of  quadrate  patches  corresponding  with  the  segments." 

Pigeons  are  affected  by  several  species  of  biting 
lice,   of   which  Goniocotes   compar  Nitzsch   is    quite 


common, 
follows : 
between 
margin. 


It  is  about  1  mm.  in  length,  described  as 
"  The  head  is  rounded  in  front,  narrower 
the  antennae,  broadest  near  the  posterior 
The  thorax  is  narrower,  the  abdomen  in 
the  male  broadest  near  the  posterior  end  and  squarish 
behind,  in  the  female  more  regular  and  broadest  near 
the  middle.  It  is  whitish,  with  a  rather  broad 
brownish  margin,  from  which  prolongations  extend 
inward  upon  the  sutures."  Another  species  said  to 
be  common  on  pigeons  is  Goniodes  damicornis  Nitzsch, 
length  2  mm. ;  in  color  it  is  brow^n.  Liyeurus  haculus 
Nitzsch  is  a  very  common  form ;  it  is  about  2  mm. 
in  length  and  exceedingly  slender  in  conformance  with 
the  generic  character.  While  the  abdomen  of  this  species  is  dark,  the 
head  and  thorax  are  reddish  brown  in  color. 


'\^i^ 


Fig.'  54.  —  A  biting 
louse  of  the  guinea 
pig,  Gyropus  ovalis. 
(Redrawn  after 
Osborn.)      X  35. 


Fig.  55.  —  Tiie  common  hen  louse,  Menopon  paZZtdum.     Male,  left;  female,  right.      X  33. 


The  commoner  lice  of  the  swan  are  Docophorus  cygni  Denny,  about 
1  mm.  in  length ;  "  in  color  the  head,  thorax  and  legs  are  bright  reddish 
brown  while  the  abdomen  is  white  in  the  center  and  dark  brown  at  the 


THE   LICE 


57 


sides,  the  brown  occupying  hard  plate-like  portions  at  the  side  of  each 
segment ; "  and  the  extremely  large  and  common  Ornithobius  hucephalus 
Piaget  (4  mm.  long).  The  latter  is  conspicuous  because  of  its  size, 
although  the  body  is  white  and  quite  transparent. 

Family  Gyropidae.  —  The  members  of  this  family  are  restricted  to 
mammals.  The  genus  Gyropus  is  a  typical  representative,  of  which 
G.  gracilis  Nitzsch  (Fig.  53),  a  long  slender  form,  is  easily  distinguish- 
able from  G.  ovalis  Nitzsch  (Fig.  54)  by  comparing  the  figures ;  both 
species  are  found  on  the  guinea  pig. 

Family  Liotheidae.  —  The  commonest  representative  of  this  family 
is  the  widely  known  chicken  louse,  Menopon  pallidum  Nitzsch  (Fig.  55). 
This  species  is  the  most  prevalent  of  all  the  hen 
lice,  is  an  active  runner,  light  yellow  in  color 
and  about  1^  to  2  mm.  in  length.  Another 
member  of  this  family,  also  infesting  chickens, 
is  Menopon  biseriatum  Piaget  (Fig.  56),  a  some- 
what larger  species,  and  considerably  less  com- 
mon. The  head  and  anus  of  young  chicks  and 
turkeys  seem  to  be  frequently  attacked  by  this 
species.  Trinoton  luridum  Nitzsch  of  ducks  is 
a  large  species  measuring  4  to  5  mm.  in  length. 
Trinoton  lituratum  Nitzsch  of  the  goose  is 
smaller  than  the  former,  considerably  lighter 
and  without  the  dark  markings. 

To  Control  Poultry  Lice.  —  The  very  fact 
that  poultry  bathe  in  dust  whenever  available 
indicates  a  potent  means  of  controlling  the  bird 
lice.  In  the  erection  of  a  modern  poultry  house 
the  dust  bath  should  be  carefully  provided  for. 
Special  boxes,  broad  and  deep  enough  so  that  there  will  be  room  for 
several  birds  at  a  time,  should  be  partly  filled  with  fine  road  dust  or 
ashes  with  the  addition  of  a  quantity  of  tobacco  dust  in  the  proportion 
of  about  six  parts  of  the  former  to  one  of  the  latter.  It  is  quite  de- 
sirable to  add  a  few  handfuls  of  sulphur.  The  finer  the  dust  the  better, 
since  the  principle  on  which  its  use  is  based  is  that  of  suffocation,  i.e.  the 
dust  particles  enter  and  clog  up  the  breathing  pores  of  the  lice.  It  is 
quite  probable  that  the  agitation  caused  by  the  dust  and  the  "wallow- 
ing "  of  the  bird  dislodges  many  of  the  lice  and  they  are  lost  in  the 
shuffle.  A  very  good  louse  powder  for  dusting  birds  by  hand  is  pre- 
pared by  mixing  gasoline,  3  parts,  and  carbolic  acid  (about  90  per  cent 
pure) ,  1  part,  and  stir  into  this  mixture  enough  plaster  of  paris  to  take 
up  the  moisture.  When  preparing  this  mixture,  it  must  be  borne  in 
mind  that  the  gasoline  is  highly  inflammable  and  that  the  carbolic  acid 
is  poisonous  and  injurious  to  the  skin.  Pyrethrum  powder  or  buhach 
(fresh)  applied  to  the  hen  directly  by  means  of  a  duster  is  also  a  good 
remedy.     A  small  handful  of  naphthaline  flakes  in  each  nest  is  very 


Fig.  56.  —  The  head  louse 
(Menopon  biseriatum)  of 
young  fowls.      X  16. 


58 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


useful.     Dipping  chickens  in  a  2  per  cent  solution  of  chlorine  is  recom- 
mended by  some. 

The  biting  lice  of  mammals  may  be  combated  as  described  below 
for  the  Pediculids. 

B.    The  Sucking  Lice 


Order  Hemiptera,  Suborder  Parasita.    Family  Pediculidoe 

Characterization.  —  With  the  characteristics  of  the  biting  lice  well 
in  mind  there  will  be  little  difficulty  in  recognizing  the  sucking  lice. 
The  members  of  this  group  are  suctorial,  blood  sucking,  and  restricted 
to  mammals.  The  proboscis  consists  of  a  long  fleshy  extensile  tube 
inclosing  three  slender  stylets.  The  mouth  parts  are  of  the  Hemip- 
teron  type  except  that  the  proboscis  is  not  jointed.  All  the  species  are 
wingless,  body  compressed,  antennae  five  jointed,  and  tarsi  are  provided 
with  strong  claws  adapted  to  hold  the  parasite  firmly  to  the  hairs  of 
its  host. 

Pediculosis.  —  An  infestation  of  lice  is  ordinarily  termed  Pedicu- 
losis, whether  it  involves  man  or  beast ;  the  term  Phthiriasis  denotes 
infestation  by  the  pubic  louse  in  particular.  Pediculosis  in  animals 
may  be  indicated  by  the  tendency  to  scratch  and  an 
effort  to  relieve  the  irritation  by  rubbing  on  rough 
objects,  such  as  fences,  posts,  etc.  These  symptoms 
may,  of  course,  indicate  the  presence  of  fleas  or  itch 
mites,  but  lousy  animals  usually  have  a  rough,  bristly 
coat,  the  eyes  being  "  wild  "  in  appearance,  the 
body  often  emaciated. 

Life  History.  — The  barrel-shaped  eggs  or  "  nits  " 
are  deposited  on  the  hairs  of  the  host  (Fig.  57)  and 
are  glued  fast  by  means  of  a  sticky  secretion.  The 
period  of  incubation  covers  commonly  from  five  to  six 
days,  the  young  insect  on  emerging  having  the  general 
appearance  of  the  adult  except  for  size.  Maturity  is 
reached  in  most  cases  in  from  three  to  four  weeks, 
which  accounts  for  the  rapid  multiplication  of  these 
parasites.  The  dissemination  of  lice  from  one  host 
to  another  is  brought  about  by  close  association  or 
by  the  indiscriminate  use  of  toilet  articles,  clothing, 
currycombs,  combs,  brushes,  etc. 

Systematic.  —  All  species  of  sucking  lice  which  inhabit  domesticated 
mammals  belong  to  the  genus  Hsematopinus.  As  is  true  in  other  genera, 
the  legs  are  short  and  thick ;  in  consequence  their  movements  are  very 
sluggish,  and  migration  from  host  to  host  is  not  easily  accomplished, 
except  in  certain  species,  such  as  the  body  lice  of  man,  which  are  rather 
active.     The  genus  Pediculus  is  restricted  to  man  and  the  anthropoid 


Fig.  57.  —  Nits  or 
eggs  of  a  sucking 
louse  attached  to 
the  hair  of  the 
host.  One  of  the 
eggs  has  hatched. 
X  10. 


THE   LICE 


59 


Fig.  58.  —  Life  history  of  the  human  head 
louse,  Pediculus  capitis,  a.  egg  ;  b.  larva  ; 
c.  male  ;  d.  female.       X  10. 


apes.  There  is  comparatively  little  structural  difference  between  its 
members.  The  genus  Phthirius  is  readily  distinguishable  from  all  other 
genera  by  its  distinctly  crablike  ap- 
pearance, broad  body  and  strong 
clasping  appendages. 

Species  affecting  Man.  —  The 
three  species  of  Pediculids  infest- 
ing man  are  cosmopolitan  and  ob- 
jects of  great  antiquity.  The  head 
louse,  Pediculus  capitis  DeG.  (Fig. 
58),  is  about  3  mm.  in  length  in 
the  female  and  about  2  mm.  in  the 
male,  varying  from  a  light  leaden 
color  to  nearly  black.  This  dif- 
ference in  color  is  said  to  corre- 
spond to  the  color  of  the  human 
host,  also  with  the  color  of  the 
hair  in  Caucasians.  Murray  ^  says, 
"  Those  of  the  West  African  and 
Australian  are  nearly  black ;  those 
of  the  Hindu,  dark  and  smoky; 
those  of  the  Africander  and  Hottentot,  orange;  those  of  the  Chinese 
and  Japanese,  yellowish  brown ;    of  the  Indians  of  the  Andes,  dark 

brown ;  of  the  Digger  Indians  of 
California,  dusky  olive,  and  those 
of  the  North  American  Indian 
near  the  Eskimo,  paler  approach- 
ing to  the  light  color  of  the  para- 
sites of  the  European."  The 
eggs  of  the  head  louse  are  quite 
conspicuous,  pear-shaped  objects, 
usually  attached  near  the  base  of 
the  hair  at  the  neck  and  back  of 
the  ears.  Fifty  is  given  by  some 
writers  as  the  number  of  eggs 
deposited  by  the  female,  and  the 
great  rapidity  of  reproduction  be- 
comes evident  when  it  is  known 
that  the  young  female  requires 
only  about  three  weeks  to  reach 
maturity.  In  bad  cases  of  pe- 
diculosis the  hair  of  the  head  may 
.^      ,„      „         ,    ,  ,  literally  become  a  mass  of  nits 

biG.  59.  —  Human  body  louse,  Peaicwms  i'es<i-  j  •, 

7nenti.     X  15.  and  parasitcs. 

1  Murray,  Andrew,  1860.     On  the  pediculi  infesting  tlie  different  races  of 
man.     Trans.  Roy.  Soc.  Edinb.,  T.  22,  p.  3,  p.  567  (cited  by  Osborn). 


X 

kW/ 

/^^; 
^»~-»- 

■IT    '. 

1' 

,:.,.->../ 

c 

J 

\ 

w 

60 


MEDICAL  AND   ^'ETERINARY  ENTOMOLOGY 


Fig. 


60.  —  The  pubic  louse,  Phthirius  ingui- 
nalis.       X  23. 


Individuals  who  have  had  experience  with  the  several  forms  of 
Pediciilids  say  that  the  head  louse  does  not  produce  the  great  discom- 
fort that  is  caused  by  the  bod}^  louse,  Pediculus  vestinienti  Leach  (Fig. 
59).     In  size  the  body  louse  is  somewhat  larger  than  the  head  louse, 

ranging  from  3  to  4  ram.  in 
length.  Size  is  not  a  good  cri- 
terion for  the  separation  of  the 
two  closely  resembling  species 
because  of  intergradation  in  the 
younger  stages.  However,  by 
comparing  the  two  species  it 
will  be  seen  that  the  antennae 
of  the  body  louse  are  relatively 
longer  and  more  slender  and 
that  the  abdomen  is  broadly 
attached  to  the  thorax.  This 
species  infests  the  clothing  of 
human  beings,  particularly  that 
worn  next  to  the  body,  where 
the  eggs  are  deposited.  Careful 
observations  on  the  life  history 
of  this  parasite  were  made  by 
Warburton  (see  NuttalP),  who  found  that  the  female  laid  124  eggs 
during  the  course  of  twenty-five  days,  and  hatched  in  eight  days  under 
favorable  conditions.  The  adult  stage  was  reached  on  the  thirteenth 
day  after  three  molts,  which  occurred  about  every  fourth  day.  Adults 
entered  into  copulation  five  days 
after  the  last  ecdysis  or  molt.  The 
adults  reared  by  Warburton  lived 
about  three  weeks  after  the  final 
molt,  and  the  "  egg  to  egg  "  period 
was  reckoned  at  about  twenty-four 
days.  Irritation  is  caused  by  suck- 
ing blood  and  by  scratching  with 
their  claws  while  crawling  about  on 
the  skin.  The  grayish  color  which 
is  characteristic  of  this  species  gives 
rise  to  the  significant  term  "  gray- 
back."  The  "  gray-back  "  is  usually 
the  unwelcome  associate  of  camp 
laborers,  soldiers  and  rangers,  and  is  commonly  looked  upon  as  a  part 
of  the  initiatory  features  of  such  life. 

If  there  is  any  possibility  of  degree  in  the  matter,  the  most  dis- 
gusting of  all  lice  infesting  human  beings  is  the  pubic  or  crab  louse. 


61.  —  Hog  louse,  Haematopinus  {urius) 
suis.      X  7. 


1  NuttaU,  G.  H.  F.,  1913.     The  Herter  Lectures  I. 
sitology,  Vol.  5,  No.  4,  pp.  271-272. 


SpirochsBtosis.    Para- 


THE   LICE 


61 


Fig.  62.  — The 
short-nosed  ox 
louse,  Hcema- 
topinus  eury- 
sternus.  (Re- 
drawn after 
Osborn.)  X22. 


Phthirius  inguinalis  Leach  (Fig.  60),  which  infests  the  pubic  region 
particularly  and  the  armpits,  rarely  other  parts.  The  ease  with  which 
this  form  is  transmitted  accounts  for  the  astonishing  abundance  and 
frequent  occurrence  of  these  parasites  on  men  in  various  stations  in 
life.  Its  identity  cannot  be  mistaken  if  the  appended 
figure  is  taken  into  account.  It  measures  from  1  to  L5 
mm.  in  length  and  is  nearly  as  broad  as  long.  The  eggs, 
not  usually  more  than  a  dozen  per  female,  are  attached 
to  the  coarse  hairs  of  the  region  infested.  The  incuba- 
tion period  lasts  from  five  to  six  days  and  full  growth 
is  reached  in  about  three  weeks. 

Species  affecting  Domesticated  Animals.  —  The  prin- 
cipal species  of  pediculi  infesting  the  domesticated  ani- 
mals belong  to  the  genus  Hsematopinus.  Each  of  these 
species  inhabits  a  specific  host,  so  that,  in  all  but  acci- 
dental cases,  the  specific  name  may  be  known  when  the 
parasite  is  taken  on  its  host,  with  only  a  good  hand  lens 
as  an  aid  to  identification.  HoBmatoyinus  suis  Linn. 
(Fig.  61)  of  the  hog  is  the  largest  representative  of  the 
genus,  measuring  as  much  as  5  to  6  mm.  in  length.  It  is  a  cosmopoli- 
tan species,  often  infesting  the  host  in  great  numbers.  It  seems  evi- 
dent, from  general  observations,  that  the  presence  of  these  parasites 
when  numerous  affects  swine  quite  seriously.  Next  to  cholera  this 
louse  is  said  to  be  the  hog's  worst  enemy.  The  head  of  the  hog  louse 
is  long,  and  together  with  the  thorax  and  abdomen  is 
provided  with  a  conspicuous  dark  border.  '  H.  {asini 
Linn.)  macrocephalus  Burm.  of  .the  horse  is  smaller  (2.5 
to  3  mm.),  otherwise  similar  in  form,  except  that  the 
head  is  relatively  longer  and  more  robust.  Cattle  may 
be  infested  with  one  of  two  species,  H.  eurysternus 
Nitzsch,  the  short-nosed  ox  louse,  or  H.  vitidi  Linn.,  the 
long-nosed  ox  louse.  The  former  is  somewhat  the  larger 
(1.5  mm.  to  2  mm.),  broader  in  proportion  and  short 
nosed  (Figs.  62-63).  The  long-nosed  ox  louse  is  said 
to  infest  the  neck  and  shoulders  in  preference  to  other 
parts.  H.  pedalis  Osb.  is  the  sheep  foot  louse,  said  by 
Osborn  to  occur  only  on  the  legs  and  feet  below  where 
the  long  wool  is  found,  and  particularly  in  the  region 
of  the  dew  claws,  where  the  eggs  appear  to  be  most 
commonly  deposited.  In  shape  it  resembles  the  long- 
nosed  ox  louse,  but  is  more  slender. 

Although  other  observers  have  found  the  sucking 
dog  louse,  H.  piliferus  Burm.,  less  common  than  the  biting  dog  louse, 
the  writer  has  found  this  species  quite  as  common  in  California  if  not 
relatively  more  abundant.  The  adults  are  about  2  mm.  in  length ; 
the  antennae  are  short  and  heavy,  as  are  the  legs,  while  the  hairy  ab- 
domen is  oval  and  usually  apparently  swollen. 


Fig.  63.  —  The 
long-nosed  ox 
louse,  Hcemato- 
pinus  vituli. 
(Redrawn  after 
Osborn.)   X  30. 


62         MEDICAL  AND  VETERINARY  ENTOMOLOGY 

Other  Species  of  Haematopinus.  —  Experiments  with  rodent  lice 
as  transmitters  of  trypanosomes  have  brought  several  of  these  species 
into  prominence,  notably  HoBiiiatopinus  sinnulosus  Biirm.  of  the  rat. 
It  is  light  yellow  in  color,  the  head  projecting  very  little  in  front  of  the 
antennae,  and  the  thorax  is  very  short.  H.  acanthojjus  Burm.  is  the 
sucking  louse  of  the  field  mouse,  while  H.  hesijeromydis  Osb.  occurs  on 
the  white-footed  mouse.  The  ground  squirrel  harbors  a  species  known 
as  //.  suturalis  Osb.,  described  by  Osborn,  viz.  "  This  species  is  particu- 
larly w'ell  marked  by  the  general  form  of  the  body  and  especially  by  the 
conspicuous  transverse  suture  back  of  the  antennae.  It  differs  further 
from  most  of  the  species  in  the  genus  in  having  both  the  anterior  and 
middle  legs  slender  and  of  nearly  the  same  size,  while  the  posterior  legs 
alone  are  especially  modified  as  clasping  organs." 

Relation  to  Disease.  —  Lousiness  may  correctly  be  designated  as 
a  disease  and  is  technically  termed  Pediculosis  or  Phthiriasis.  This 
applies  equally  well  to  either  the  biting  or  sucking  lice.  While  the 
presence  of  lice  on  the  body  of  an  animal  may  not  result  in  serious  conse- 
quences, nor  even  in  much  discomfort,  an  abundance  of  these  parasites 
naturally  results  in  a  weakened  condition,  predisposing  the  host  to  other 
diseases  through  loss  of  blood  (when  infested  wdth  sucking  lice)  and 
general  irritation  resulting  in  poor  digestion.  Intense  irritation, 
pruritus,  on  the  trunk  of  the  body  in  human  beings  is  often  the  result 
of  body  lice.  Furthermore,  it  is  quite  certain  that  infection  may  be 
transmitted  from  animal  to  animal  (of  the  same  species)  by  lice,  either 
upon  feet  and  mouth  parts,  as  the  bee  carries  pollen,  e.g.  impetigo,  or 
within  their  bodies,  as  explained  under  spirochcetosis. 

Impetigo.  —  In  the  human  such  diseases  as  Impetigo  and  Favus  may 
be  transmitted  by  the  pediculi.  Tropical  impetigo  {Pemphigus  contagi- 
osus)  is  said  to  be  caused  by  Diplococcus  pem.phigi  contagiosi  Wherry, 
while  favus  is  traceable  to  a  fungus  variously  classified,  probably  best 
known  as  AcJwrion  schoenleini.  The  following  experiments  cited  from 
Nuttall/  bear  evidence  to  the  transmission  of  impetigo  :  "Dew^evre  (1892) 
claims  that  pediculi  disseminate  impetigo.  He  removed  ten  pediculi 
from  a  child  suffering  from  impetigo  and  placed  them  on  a  healthy 
infant,  which  a  few  days  later  developed  impetigo.  The  experiment 
was  repeated  several  times  with  the  same  results.  In  a  second  series 
of  experiments,  he  took  scrapings  from  under  the  nails  of  children  that  had 
impetigo,  and  placing  them  on  artificially  scratched  places,  reproduced 
the  disease.  Lastly  he  took  pediculi  from  a  child  that  was  not  affected 
with  impetigo  and  placed  them  on  a  child  that  had  the  disease;  removing 
them  after  twenty  minutes,  he  replaced  them  on  a  healthy  child.  The 
latter  acquired  the  disease,  as  did  fifty  per  cent  of  the  children  so  experi- 
mented wuth.  He  claims  the  specific  microorganism  adheres  to  the 
front  legs  especially,  also  to  the  hairs  of  the  insect,  and  the  latter 
carries  them  as  bees  do  pollen.  In  the  last  set  of  experiments,  he  only 
1  NuttaU,  G.  H.  F.,  1899  {loc.  cil.). 


THE   LICE 


63 


4T& 


Fig.  64.  — •  Smear  preparation  show- 
ing Treponema  pallidum  of  syph- 
ilis.    (Greatly  enlarged.) 


allowed  the  pediculi  to  remain  half  an  hour  on  the  healthy  head,  but 
this  was  sufficient  to  produce  infection."  The  above  typical  example 
also  illustrates  the  methods  used  to  secure  the  experimental  evidence  of 
transmission. 

SpirochaBtosis.  —  An  infection  of  spirochetes  is  known  as  spiro- 
chcetosis.  The  spirochaetae  are  protozoa  belonging  to  the  class  Zoomasti- 
gophora  (Flagellata),  order  Spirochsetida. 
They  consist  of  undulated  filamentous 
bodies,  in  some  of  which  there  is  said  to 
be  present  a  narrow  membrane  extend- 
ing from  end  to  end  of  the  body.  In 
the  genus  Treponema,  e.g.  Treponema 
pallidum  Schaudinn  (Fig.  64)  of  syphilis, 
the  membrane  is  absent  and  the  body  is 
strongly  spiral ;  in  the  genus  Spirochseta, 
e.g.  Spirochceta  novyi  (Shellack),  the  body 
is  wavy  or  undulatory  (Fig.  65). 

Both  man  and  beast  are  affected  by 
SpirochcBtosis,  but  in  the  former  the  term 
relapsing  fever  is  ordinarily  applied.  The 
relapsing  fevers  are  characterized  by 
fevers  sudden  in  appearance  and  rather  sudden  in  subsidence,  with 
relapses  at  irregular  and  indefinite  intervals.  The  mortality  is  given 
at  about  5  per  cent.  Relapsing  fever  is  most  likely  to  be  confused  with 
malaria  but  for  the  characteristics  above  mentioned  and  the  presence 
of  spirochsetes  in  greater  or  less  number  in  the  blood  of  the  patient. 

The  African  relapsing  fever,  traceable  to 
SpirochcBta  duttoni  (Novy  and  Knapp),  is 
transmitted  by  ticks;  while  the  European 
form,  traceable  to  Spirochwta  recurrentis 
(Lebert),  the  American  form  {Spirochceta 
novyi  Shellack)  and  the  Indian  form  {Spi- 
rochceta  carteri  Mackie)  are  transmitted  by 
the  pediculi,  as  later  described. 

The  first  important  evidence  to  the  effect 
that  lice  may  be  concerned  in  the  trans- 
mission of  relapsing  fever  was  advanced  by 
Mackie^  in  India  in  1907,  who  records  an 
outbreak  of  the  disease  among  school  chil- 
dren, in  which  137  out  of  170  boys  and  35 
out  of  114  girls  were  attacked.  Twenty-four  per  cent  of  the  lice  re- 
moved from  the  boys  contained  spirochsetes,  while  only  3  per  cent  of 
the  lice  removed  from  the  girls  were  infected.  As  the  parasites  in- 
creased in  abundance  among  the  girls,  so  also  did  the  epidemic  increase, 


Fig.  65.  —  Spirochceta  novyi  in 
a  blood  smear.  (Greatly  en- 
larged.) 


1  Mackie,  F.  P.,  1907. 
mission  of  relapsing  fever. 


The  part  played  by  Pediculus  corporis  in  the  trans- 
British  Med.  .Journ.2  1907,  p.  1706. 


64         MEDICAL  AND    VETERINARY   ENTOMOLOGY 

and  conversely  as  the  parasites  became  less  abundant  among  the  boys, 
so  also  did  the  epidemic  decrease.  The  spirochsetes  were  observed  to 
multiply  in  the  intestine  of  the  lice  and  were  found  to  be  present  in 
the  ovaries,  testes  and  Malpighian  tubules.  Mackie  concluded  that 
infection  might  be  spread  by  the  lice  by  regurgitating  the  spirochsetes 
into  the  wound  produced  by  the  bite. 

Later  (1912)  Nicolle,  Blaizot  and  ConseiF  failed  to  transmit  the 
spirochetes  through  the  bites  of  infected  lice,  and  found  that  the  only 
reliable  successful  experiments  involved  the  injection  or  subcutaneous 
inoculation  of  an  extract  of  infected  lice. 

Based  on  experiments  in  which  men  and  monkeys  were  exposed  to 
hundreds  of  bites,  Nicolle  and  his  colleagues  came  to  the  conclusion  that 
transmission  is  brought  about  by  the  introduction  of  spirochsetes  re- 
ceived under  the  finger  nails  and  on  the  finger  tips  from  crushed  parasites, 
which  are  inoculated  into  excoriated  skin  in  scratching.  They  also 
found  that  the  spirochaetes  disappear  and  later  reappear,  only  a  few 
remaining  in  the  insect's  intestine  up  to  five  or  six  hours  after  infection, 
and  none  after  twenty-four  hours,  but  reappear  in  the  insect  in  from 
eight  to  twelve  days  and  are  then  present  in  the  general  body  cavity, 
none  being  found  in  the  alimentary  canal.  It  was  also  found  that  the 
spirochaetes  are  transmitted  to  the  offspring  of  infected  lice. 

The  incubation  period  in  the  human  is  said  to  be  from  seven  to  ten 
days. 

Typhus  Fever.  —  Typhus  fever,  known  also  as  tarbardillo  (Mexico), 
Brill's  disease  (United  States),  jail  fever  or  war  fever,  is  a  disease  of 
ancient  origin  and  wide  distribution.  The  disease  is  characterized  by 
a  high  fever,  backache,  headache,  bronchial  disturbances,  congested  face 
(designated  also  as  a  "  besotted  expression  "),  brick-red  mottled  eruption 
which  later  spreads,  becoming  brownish  irregular  blotches.  This 
spotting  led  to  the  belief  that  tarbardillo  of  Mexico  was  identical 
with  spotted  fever  of  Montana,  a  fact  proved  untrue  by  Ricketts,  who 
lost  his  life  by  typhus  fever  during  the  course  of  his  investigation. 
Experiments  and  observations  by  Nicolle  and  Ricketts  and  Wilder  ^ 
indicate  that  the  bedbug  and  the  flea  are  not  instruments  of  trans- 
mission. That  the  body  louse  {Pediculus  vestimenti)  is  the  most  impor- 
tant, if  not  sole  agent,  in  the  transmission  of  typhus  fever  has  been  proved 
by  Nicolle  et  al.^  (1909,  working  in  Tunis)  and  Ricketts  and  Wilder^ 

1  Nicolle,  C.  N.,  Blaizot,  L.,  and  Conseil,  F.,  1913.  Ann.  Inst.  Pasteur, 
March  25,  1913,  pp.  204-225. 

2  Ricketts,  H.  T.,  and  Wilder,  R.  N.,  1910.  Further  investigations  regard- 
ing the  etiology  of  tarbardillo,  Mexican  typhus  fever.  Journ.  Amer.  Med.  Assoc, 
Vol.  55,  No.  4,  pp.  309-311. 

^  NicoUe,  Charles,  Comte,  C,  et  Conseil,  E.,  1909.  Transmission  experi- 
mentale  du  typhus  exanthimatique  par  le  pou  du  corps.  Paris  Acad.  Sc. 
Comptes  Rendus,  T.  149,  pp.  486-489. 

*  Rickets,  H.  T.,  and  Wilder,  R.  M.,  1910.  The  transmission  of  the  typhus 
fever  of  Mexico  (tarbardillo)  by  means  of  the  louse  (Pediculus  vestimenti). 
Journ.  Amer.  Med.  Assoc,  Vol.  54,  No.  16,  pp.  1304-1307. 


THE   LICE  65 

(1910,  working  in  Mexico).  The  latter  found  that  Macacus  rhesus  can 
be  infected  with  tarbardillo  (Mexican  typhus)  invariably  by  the  in- 
jection of  virulent  blood  from  man  taken  on  the  eighth  to  tenth  day 
of  fever,  that  the  monkey  may  pass  through  an  attack  of  typhus  so 
mild  that  it  cannot  be  recognized  clinically  and  that  vaccination  results. 
Typhus  was  transmitted  to  the  monkey  by  the  bite  of  the  louse  in  two 
experiments,  the  lice  in  one  instance  deriving  their  infection  from  man 
and  in  another  from  the  monkey.  Another  monkey  was  infected 
through  the  introduction  of  the  feces  and  abdominal  contents  of  infected 
lice  into  small  incisions.  The  causative  microorganism  of  typhus  is 
claimed  by  Plotz  to  be  a  small  Gram  positive,  pleomorphic  bacillus. 

The  incubation  period  in  the  human  is  from  ten  to  twelve  days. 
The  duration  of  the  disease  is  said  to  be  about  twelve  days  in  children,  in 
which  it  is  usually  comparatively  mild,  to  twenty-one  to  twenty-four  days 
in  adults.  The  mortality  is  said  to  range  from  15  per  cent  to  30  per  cent, 
but  may  be  as  high  as  50  per  cent  to  75  per  cent  under  war  conditions. 

Rat  Trypanosomiasis.  — •  A  relatively  common  and  apparently  non- 
pathogenic protozoan  parasite  of  the  rat  is  Trypmiosoina  lewisi  Kent. 
Various  observers,  among  them  Brumpt  and  Minchin  and  Thomson, 
have  determined  that  this  trypanosome  is  transmitted  by  the  rat  louse, 
Hoematopinus  spinulosus,  in  w^hich  host  the  protozoon  undergoes  certain 
developmental  changes.  Other  insect  hosts  of  the  trypanosome  are 
known,  among  them  the  rat  flea,  Ceratophyllus  fasciatus. 

Relation  to  TaBniasis.  —  Dipylidium  caninum  Linn.  (Tcenia  cucu- 
merina),  the  double-pored  dog  tapeworm,  is  a  common  parasite  of  the 
dog  and  is  occasionally  found  in  humans,  especially  children.  It  meas- 
ures from  ten  to  fourteen  inches  in  length,  has  long  seedlike  pro- 
glottides and  an  armored  scolex,  and  has  as  its  larval  host  the  biting 
dog  louse,  Trichodedes  lotus}  The  larva  or  bladder  worm,  known  as 
Cysticercus  trichodedes,  has  been  experimentally  produced'  in  the  louse 
by  placing  ripe  crushed  proglottides  of  the  tapeworm  on  the  skin  of  a 
dog  infested  with  lice. 

As  has  already  been  explained,  the  biting  lice  subsist  on  epidermal 
scales,  skin  exudations  and  other  matter  on  the  skin  of  the  animal. 
This  habit  makes  it  comparatively  easy  for  the  louse  to  become  infected 
through  eggs  in  the  kennel  in  which  the  dog  lies.  The  dog,  on  the  other 
hand  readily  infects  himself  by  devouring  the  lice  which  irritate  his  skin. 

Persons,  particularly  children,  while  fondling  louse-infested  dogs 
may  easily  become  infected  by  accidentally  swallowing  lice  which  con- 
tain bladder  worms.  This  is  more  readily  accomplished  if  the  person 
is  eating  at  the  time. 

How  Lice  are  Disseminated.  —  The  most  effective  means  for  the 
distribution  of  lice  on  humans  is  the  indiscriminate  use  of  toilet  articles, 
garments  and  bedding  ;  also  close  association.     The  mere  presence  of  lice 

1  Occurs  also  in  the  dog  flea,  Ctenocephalus  canis,  and  in  the  human  flea, 
Pulex  irritans. 


66         MEDICAL  AND  VETERINARY  ENTOMOLOGY 

does  not  invariably  indicate  uncleanly  habits,  but  the  continued  presence 
of  these  parasites  is  inexcusable.  Cases  have  come  under  the  observa- 
tion of  the  Avriter  in  which  several  members  of  a  highly  respectable 
family  were  sadly  infested  with  the  head  louse,  to  their  great  dismay. 
Members  of  this  family  were  greatly  alarmed,  believing  themselves 
disgraced  for  all  time.  The  infestation  was  thus  explained.  It  was 
found  that  a  maid  employed  by  the  family  had  previously  been  engaged 
by  another  family  whose  children  became  infested  in  school,  as  may 
happen.  In  caring  for  the  children  the  maid  in  turn  became  infested 
and  shortly  thereafter  sought  another  position,  which  was  found  with 
the  family  in  question.  By  indiscreet  use  of  combs  and  brushes  a 
general  infestation  was  inevitable. 

Domesticated  animals  may  have  lice  communicated  to  them  by 
close  association,  especially  in  the  winter  time,  and  by  infected  curry 
combs,  blankets  and  similar  articles,  also  by  rubbing  on  stalls,  fences, 
etc.  against  which  infested  animals  have  previously  rubbed  themselves. 

Treatment.  —  Personal  cleanliness  is  by  far  the  best  method  to 
prevent  lice  from  gaining  a  foothold;  however,  the  exception  has  al- 
ready been  indicated.  The  mere  use  of  water  is  ineffective  in  destroying 
vermin  present  in  the  hair,  and  the  "  nits  "  are  even  more  difficult  to 
destroy.  In  the  case  of  the  body  louse,  a  clean  body  would  not  prevent 
reinfestation  if  the  same  underclothing  are  put  on  in  the  absence  of  a 
change,  which  often  occurs  where  men  are  necessarily  far  removed  from 
civiUzation  or  are  under  accidental  conditions. 

To  free  the  head  of  lice  a  fine-tooth  comb  dipped  in  any  hair  pomade 
containing  oil  may  be  used.  Dipping  the  comb  in  ordinary  kerosene 
before  applying  to  the  head  is  a  method  frequently  employed  with  good 
results.  Several  families  in  which  this  method  has  been  followed  under 
the  writer's  observation  were  completely  freed  of  the  parasites  in  that 
manner,  with  at  least  no  apparent  injury  to  the  hair,  an  objection  some- 
times raised.  The  oil  coming  in  contact  with  the  lice  kills  them,  but 
the  eggs  or  nits  cannot  be  destroyed  so  well;  therefore  the  combing 
process  must  be  repeated  three  times  at  intervals  of  one  week  in  order 
to  destroy  the  newly  hatched  lice  and  thus  prevent  fresh  propagation. 
Care  should  be  exercised  in  removing  the  parasites,  so  that  further 
dissemination  does  not  occur.  A  good  method  is  to  use  a  black  oil- 
cloth or  slate  upon  which  the  combings  are  placed  and  the  parasites 
certainly  destroyed  by  an  application  of  kerosene.  The  whitish  para- 
sites can  readily  be  seen  on  the  black  background  and  none  need  escape. 
Washing  the  head  in  a  2  per  cent  solution  of  creolin  is  also  effective  if 
repeated  as  above.  Winding  the  head  in  long  towels  wet  with  tincture  of 
larkspur  (Delphinium),  10  per  cent,  is  strongly  recommended  by  many. 

The  heads  of  children  with  long  hair  may  be  treated  success- 
fully in  the  following  manner,  as  described  by  Whitfield  in  the 
Lancet  (Dec.  14,  1912).  The  child  is  placed  on  its  back  in  a  bed,  with 
the  head  hanging  over  the  edge,  so  that  the  hair  falls  in  a  basin  resting 


THE  LICE  67 

on  a  chair.  The  sokition  to  be  used  (the  author  recommends  Phenol 
12  grams  and  water  500  grams)  is  poured  over  the  hair  and  carefully 
washed  back  and  forth  for  a  period  of  ten  minutes  until  the  hair  is  well 
soaked',  particularly  back  of  the  ears  and  the  nape  of  the  neck.  After- 
wards the  hair  is  drained,  not  wrung  out,  however,  and  is  then  put  up 
with  a  towel  or  flannel  cloth  in  turban  fashion.  After  an  hour  the  hair 
may  be  washed  out  or  simply  left  to  dry,  when  it  will  be  found  that  all 
the  pediculi  as  well  as  the  ova  have  been  destroyed. 

Body  lice  can  only  be  controlled  by  treating  the  clothing  and  bedding 
of  the  person  infested.  A  favorable  abode  is  provided  by  the  folds  and 
hems  of  undergarments  where  the  eggs  are  deposited  and  where  a 
lively  existence  is  manifested.  Consequently  the  necessity  for  a  com- 
plete stripping  off  of  all  w^earing  apparel  to  the  smallest  detail  becomes 
apparent.  All  garments  should  then  be  at  once  subjected  to  a  baking, 
steaming  or  fumigating  process;  the  undergarments  may  be  boiled. 
Soaking  all  garments  in  gasoline  or  benzine  is  also  recommended. 
It  is  suggested  that  this  is  the  simplest  process  as  it  kills  all  the  adults 
at  once,  and  if  it  can  be  repeated  at  short  intervals,  the  clothing  can 
be  worn  in  the  period  between  treatments.  The  extreme  irritation 
caused  by  body  lice  may  be  relieved  by  the  application  of  a  lotion 
of  one  half  ounce  of  borax  to  a  pint  of  water. 

In  dealing  with  lice  under  typhus  fever  conditions  the  greatest  care 
must  be  exercised  owing  to  the  minuteness  of  the  parasites  and  the 
great  danger  from  infection.  The  patient  must  be  completely  stripped 
in  a  special  room,  placing  his  garments  at  once  in  a  vessel  and  covering 
them  immediately  with  benzine  or  gasoline.  The  face  and  head 
must  be  shaved  and  the  hair  burned  at  once.  All  instruments  must 
be  carefully  sterilized. 

The  liberal  use  of  kerosene  on  floors  and  beneath  cots  is  strongly 
urged.  Rubbing  the  body  with  kerosene  acts  as  a  good  preventive ; 
the  use  of  flowers  of  sulphur  has  also  been  recommended. 

The  pubic  louse,  easily  disseminated,  is  also  easily  eradicated  be- 
cause of  its  local  occurrence  in  both  the  adult  stage  and  the  egg.  How- 
ever, notwithstanding  the  ease  of  locating  them,  they  are  extremely 
tenacious,  and  repeated  applications  of  the  remedy  must  be  resorted  to. 
Mercurial  ointment  (blue  ointment)  applied  as  a  salve  to  the  parts 
affected  is  commonly  used.  The  proportions  recommended  are  two 
parts  of  mercurial  ointment  and  one  part  petrolatum.  The  use  of 
mercurial  ointment  directly  after  a  bath  may  produce  bad  results,  and 
furthermore  the  salve  is  not  to  be  strongly  rubbed  in.  Tincture  of 
larkspur  (Delphinium)  10  per  cent  is  recommended  or  also  10  per  cent 
solution  of  fishberry  and  alcohol  or  just  plain  kerosene.  All  treatments 
must  be  repeated  at  least  three  times  at  intervals  of  about  one  week 
in  order  to  destroy  larvse  newly  emerging  from  eggs  not  attacked  by 
the  chemicals.  An  application  of  vinegar  makes  the  eggs  more  suscept- 
ible to  the  treatment. 


68         MEDICAL  AND   VETERINARY  ENTOMOLOGY 

Control  on  Animals.  —  When  domesticated  animals  are  lousy,  their 
quarters  must  be  thoroughly  cleaned  and  disinfected,  together  with 
currycombs  and  similar  articles.  The  latter  may  be  dipped  in  kerosene 
or  crude  oil.  Cattle,  sheep  and  hogs  may  be  dipped,  sprayed  or  hand 
dressed  with  tobacco  decoctions.  Owing  to  differences  in  nicotine 
content  tobacco  dips  must  be  used  as  specifically  directed.  Creohn, 
2  per  cent  for  dogs,  cats,  monkeys,  and  4  per  cent  for  hogs  is  useful ; 
kerosene  emulsion  (10  per  cent  for  hogs),  tincture  of  larkspur  10  per 
cent,  or  other  remedies  such  as  Ivreso,  Chloronaphtholeum,  etc.,  as  spe- 
cifically directed.  Horses,  of  course,  should  not  be  dipped,  but  may  be 
treated  with  creolin  2  per  cent  or  kerosene  emulsion  10  per  cent,  or 
other  remedies  above  mentioned  by  local  applications  with  rub  rags  or 
currycomb.  Kerosene  in  any  form  should  not  be  applied  to  animals 
in  the  hot  sunshine.  All  treatments  for  lice  must  be  repeated  at  least 
three  times  at  intervals  of  about  a  week  to  ten  days  in  order  to  destroy 
the  young  lice  emerging  from  eggs  not  destroyed  by  chemicals.  It  is 
advisable  to  add  creolin  to  hog  wallows  from  time  to  time,  a  measure 
which  proves  very  useful  in  keeping  the  animals  comparatively  free  from 
lice. 

Fumigation  for  lice  is  seldom  practiced,  because  of  the  special  equip- 
ment necessary  and  time  required  for  the  operation.  Osborn  has 
successfully  used  fumigants  in  the  control  of  the  short-nosed  ox  louse. 
In  his  experiments  the  animal  was  placed  in  a  tight  box  stall,  one  end 
having  a  close-fitting  door  to  admit  the  largest  animal  to  be  treated, 
the  opposite  end  a  stanchion  in  which  the  animal  is  fastened.  An 
opening  at  the  stanchion  end  of  the  stall  is  made  for  the  animal's  head 
to  protrude,  and  is  surrounded  by  a  sack-like  covering  open  at  both 
ends,  the  inner  end  nailed  to  the  opening  and  the  other  made  to  fit 
tightly  around  the  head  just  in  front  of  the  horns,  thus  exposing  the 
eyes  and  nose  to  the  air.  The  fumigating  substance  is  introduced 
into  the  stall  through  an  opening  at  the  side  near  the  bottom.  Osborn 
used  tobacco,  which  was  placed  on  a  wire  screen  over  a  tin  trough  con- 
taining alcohol.  He  states  that  it  should,  however,  be  burned  with 
coals  or  by  using  a  small  quantity  of  kerosene.  One  or  two  ounces  of 
tobacco  and  an  exposure  of  twenty  to  thirty  minutes  was  found  effective. 
He  also  adds  that  pyrethrum  might  even  be  better  than  tobacco.  The 
time  of  exposure  necessary  will  vary. 


CHAPTER  VIII 
BEDBUGS  AND  CONE-NOSES 

A.  The  Bedbugs 
Order  Hemiptera,  Family  Cimicidae 

Characterization.  —  Members  of  the  family  Cimicidse  (Acanthiidse) 
are  extremely  flattened  in  form,  fitted  to  crawl  in  narrow  crevices.  As 
adults  they  are  reddish  brown  in  color  and  wingless  but  for  the  merest 
pads  and  are  possessed  of  a  characteristic  pungent  odor  which  when 
once  noted  will  be  easily  recognized  thereafter.  The  mouth  parts 
of  this  family  are  of  the  typical  Hemipteron  type ;  they  are  three-seg- 
mented and  inclose  long  slender  stylets.  The  Aradidse,  or  flat  bugs, 
in  their  younger  stages  are  often  mistaken  for  Cimicidse.  The  bed- 
bugs are  normally  intermittent  parasites,  but  may  undergo  long  periods 
of  starvation,  at  least  one  year. 

Systematic. — ^The  family  Cimicidse  belongs  to  the  Order  Hemiptera, 
which  is  subdivided  into  three  divisions  or  suborders :  (1)  Heteroptera, 
in  which  the  forward  pair  of  wings,  when  present,  are  thick  and  leathery 
(coriaceous)  proximally,  and  membranous  distally;  the  mouth  parts 
are  free  and  the  long  axis  of  the  head  forms  a  straight  line  with  the 
body,  e.g.  Cone-noses  (Ruduviidse),  Squash  bugs  (Coreidse)  and  Bed- 
bugs (Cimicidse) ;  (2)  Homoptera,  in  which  the  wing  covers,  when 
present,  are  membranous  throughout  and  the  mouth  parts  may  or 
may  not  be  fused  to  the  thorax,  while  the  long  axis  of  the  head  forms 
a  right  angle  with  the  body,  e.g.  Cicadas  (Cicadidse),  Leaf  hoppers 
(Membracidse)  and  Plant  lice  (Aphididse) ;  (3)  Parasita,  which  includes 
the  sucking  lice  (Pediculidse)  already  considered. 

The  three  principal  genera  of  the  family  Cimicidse  ^  are  (1)  Cimex, 
in  which  the  rostrum  is  short,  reaching  about  to  the  anterior  coxse ; 
body  covered  with  short  hairs,  only  the  lateral  sides  of  pronotum  and 
elytra  fringed  with  longer  hairs;  antennse  with  the  third  and  fourth 
joints  very  much  thinner  than  the  first  and  second  and  capillary;  (2) 
QEciacus,  in  which  the  body  is  clothed  with  long  silky  hairs ;  third  and 
fourth  joints  of  the  antennse  only  a  little  thinner  than  the  first  and  second 
and  filiform ;  (3)  Hsematosiphon,  in  which  the  rostrum  is  long,  reaching 
to  the  posterior  coxse. 

The  genus  Cimex,  among  others,  is  represented  by  the  common  bed- 

^  Horvath,  G.,  1912.  Revision  of  the  American  Cimicidse.  Annales  Musei 
Nationalis  Hungarici,  Vol.  X,  pp.  257-262. 

69 


70 


MEDICAL  AND   VETERINARY   ENTOMOLOGY 


bug,  C.  lectularius  Linn.;  it  has  the  body  covered  with  short  hairs; 
the  second  joint  of  the  antennae  is  shorter  than  the  third.  C.  pilosellus 
Horv.  is  a  parasite  of  bats  (C.  i)ipistrelli  Jenyns  is  European) ;  it  has 
the  body  covered  with  longer  hairs,  and  the  second  and  third  antennal 
joints  equal  in  length.  C.  hemipterus  I'abr.(  =  C.  rotundatus  Patton  = 
C.  macrocephalus  Kirk.)  is  a  parasite  of  man  and  poultry  as  well;  it 
occurs  in  Africa,  Asia,  South  America  and  Jamaica.  In  this  species 
the  lateral  sides  of  the  pronotum  are  dilated,  not  reflexed,  fringed 
with  less  dense  and  nearly  straight  hairs,  elytra  with  the  apical 
margin  distinctly  rounded  (Horvath). 


Fig. 


66.  —  The  common  bedbug,  Cimex  lectularius.     Male,  left ;  female,  right.    Also  shows 
piercing  stylets  exposed.       X  10. 


The  genus  (Eciacus  is  represented  by  the  European  barn  swallow  bag, 
0.  hirunclinus  Jenyns,  and  0.  vicarius  Horv.,  the  corresponding 
American  species. 

HoBmatosiphon  inodorus  Duges  is  the  only  known  species  of  this 
genus,  and  infests  poultry  in  Mexico  and  southwestern  United  States. 
The  generic  characters  already  referred  to  serve  to  distinguish  this 
species. 

The  Common  Bedbug.  —  The  common  adult  bedbug,  Cimex 
lectularius  Linn.  (Fig.  66),  measures  from  4  to  5  mm.  in  length,  3  mm.  in 
breadth,  is  obovate  in  form  and  much  flattened.  The  adult  is  reddish 
brown  in  color,  though  the  young  insects  are  yellowish  white.  Among 
the  local  names  applied  to  these  insects  are  "  chinches,"  "  chintzes," 
"  red  coats,"  "  mahogany  flats,"  "  wall  louse,"  "  bedbugs  "  or  simply 
"  bugs." 

Bedbugs,  like  the  lice,  have  been  the  constant  companions  of  man 


BEDBUGS  AND   CONE-NOSES  71 

for  centuries,  —  the  earliest  writings  on  Natural  History  (Pliny  and 
Aristotle)  make  mention  of  them. 

Habits  and  Life  History.  —  Bedbugs  are  nocturnal  in  their  feeding 
habits,  hiding  in  crevices  during  the  day.  At  night  they  are  very  active, 
crawling  out  of  their  hiding  places  often  to  travel  considerable  distances 
to  attack  their  victims.  This  is  especially  true  where  iron  bedsteads 
are  used  which  do  not  provide  convenient  hiding  places  for  the  bugs. 
Ordinarily  where  the  old-fashioned  wooden  bedsteads  are  used  the 
bugs  stay  closer  to  their  point  of  attack.  They  are  gregarious,  hence 
often  great  assemblages  may  be  found  in  some  convenient  cre\ice.  In 
such  situations  the  eggs  are  usually  deposited. 

The  females  deposit  from  75  to  200  rather  large  yellowish  white  eggs 
easily  visible  to  the  naked  eye.  As  in  many  Hemiptera,  often  only 
very  few  eggs  are  deposited  at  a  time  and  oviposition  occurs  at  intervals 
during  a  period  of  from  two  to  three  months.  The  period  of  oviposition 
is  apparently  limited  to  the  spring  and  summer  months,  notwithstanding 
the  fact  that  the  insects  are  commonly  favored  by  warm  rooms  during 
the  winter.  The  eggs  are  whitish  in  color  and  distinctly  reticulated. 
The  young,  which  have  the  general  form  of  the  adults  (therefore  simple 
in  their  metamorphosis),  hatch  in  from  five  to  twelve  days,  influenced 
by  temperature,  however,  as  is  their  later  growth.  Thus  the  results  of 
experiments  and  observations  of  writers  differ  greatly  with  regard  to 
the  life  history.  The  time  required  for  development  from  the  egg  to 
maturity  is  given  at  from  forty-five  days  to  eleven  months  and  there 
may  be  two  or  more  generations.  Ordinarily  eight  to  ten  weeks  are 
required  to  reach  maturity.  The  presence  or  absence  of  food  influences 
this  period  greatly.  Marlatt  ^  has  shown  that  bedbugs  molt  five  times 
and  that  the  minute  wing  pads  make  their  appearance  with  the  last 
molt.  He  also  found  that  ordinarily  but  one  meal  is  taken  between 
each  molt  and  one  before  egg  deposition  and  that  an  average  period  of 
eight  days  is  required  between  moltings. 

Methods  of  Distribution.  —  Bedbugs,  like  lice  or  any  other  organism, 
cannot  originate  spontaneously  in  filth  as  is  believed  by  many ;  they 
must  be  introduced  in  some  manner,  either  in  the  form  of  eggs,  young 
or  adults.  Thus  the  introduction  of  one  impregnated  female  might 
furnish  the  nucleus  for  a  well-developed  colony  of  bedbugs  inside  of  a 
few  months.  Hence  the  best  regulated  household  is  not  exempt  from 
invasion,  though  cleanliness  is  the  best  preventive  against  the  multipli- 
cation of  any  household  pest. 

Public  conveyances  are  commonly  means  for  the  dissemination  of 
bedbugs.  As  Smith  ^  has  well  said,  "  I  have  seen  them  in  railroad 
cars,  trolleys,  boats,  omnibuses  and  carriages,  and  have  noted  them 

1  Marlatt,  C.  L.,  1902.  The  Bedbug.  Giro.  No.  47,  Second  Series,  U.  S. 
Dept.  of  Agric,  Div.  of  Entomology. 

2  Smith,  John  B.,  1909.  Our  Insect  Friends  and  Enemies.  J.  B.  Lippin- 
cott  Co.,  314  pp. 


72  MEDICAL  AND   VETERINARY  ENTOMOLOGY 

crawling  on  the  clothing  of  well-dressed  fellow  passengers  who  probably 
did  not  bring  them  in."  Furthermore,  migration  from  house  to  house 
by  way  of  water  pipes,  walls  and  the  like  is  not  at  all  unlikely  when  in- 
fested houses  are  vacated  and  the  food  supply  is  cut  off.  They  are  also 
easily  carried  in  clothing,  traveling  bags,  suit  cases,  etc. 

Bedbug  Bites.  —  Persons  "  bitten  "  by  bedbugs  are  differently 
affected ;  in  some  the  bite  produces  marked  swellings  and  considerable 
irritation,  while  in  others  not  the  slightest  inconvenience  is  caused. 
(The  same  condition  is  found  in  the  case  of  flea  bites  and  mosquito 
bites.)  The  bite,  so  called,  of  the  bedbug  is  produced  by  puncturing 
organs  of  the  Hemipteron  type  already  described.  It  is  probable  that 
the  pierce  of  these  stylets,  unattended  by  contamination  or  specific 
poisons,  would  produce  little  pain.  The  local  irritation  and  swelling 
is  unquestionably  produced  by  a  specific  poison  of  alkaline  reaction 
secreted  by  the  salivary  glands  and  introduced  in  the  act  of  feeding. 

The  fact  that  the  bedbug  is  obliged  to  feed  at  least  five  different 
times  either  upon  the  same  or  a  different  host,  —  the  latter  being  the 
case  most  probably  in  rooming  houses,  hotels  and  crowded  dwellings, 
—  leads  to  the  question  of  disease  transmission. 

Disease  Transmission.  —  In  consequence  of  statements  made  by 
a  number  of  authors  that  the  bedbug  is  capable  of  transmitting  plague 
and  other  septicsemic  infections,  Nuttall  ^  carried  on  a  series  of  ex- 
periments with  these  insects.  Mice  were  used  in  these  experiments 
because  they  are  very  susceptible  to  the  affections  in  question.  He 
allowed  the  bugs  to  bite  mice  which  had  just  died  or  were  dying  of 
anthrax,  plague  and  mouse-septicaemia  and  then  transferred  them 
to  healthy  mice.  Nuttall's  experiments  with  anthrax  are  particularly 
instructive.  Mice  inoculated  with  anthrax  died  in  from  eighteen  to 
twenty-four  hours,  after  which  they  were  placed  in  glass-covered  dishes 
and  hungry  bugs  introduced.  As  soon  as  the  bugs  had  sucked  a  little 
blood  they  were  removed  to  test  tubes  by  means  of  a  small  camel's- 
hair  brush  and  transferred  to  a  shaved  spot  on  healthy  mice,  by  in- 
verting the  tubes.  Eight  mice  bitten  by  124  infected  bugs  all  remained 
healthy.  Variations  of  this  experiment  gave  similar  results.  It  was 
found  that  the  anthrax  bacilli  die  in  the  stomach  of  the  insect  in 
forty-eight  to  ninety-six  hours  at  13°  to  17°  C.  and  in  twenty-four 
to  forty-eight  hours  at  37°  C,  and  that  the  feces  from  the  bugs  con- 
tained living  bacilli  during  the  first  twenty-four  hours  after  feeding. 
In  view  of  these  experiments  it  may  be  concluded  that  infection 
through  the  bite  of  a  bedbug  either  does  not  occur  or  is  exceptional. 
That  infection  might  occur  if  recently  infected  bugs  were  crushed  while 
feeding  and  the  punctured  parts  scratched  is  to  be  expected. 

Kala  Azar.  —  Kala  azar  or  dumdum  fever  is  a  highly  fatal  protozoal 
disease  of  India,  having  in  many  respects  some  similarity  to  malignant 
ague,  but  does  not  respond  to  quinine.  The  causative  organism, 
1  NuttaU,  1899  {loc.  ciL). 


BEDBUGS  AND   CONE-NOSES  73 

Leishmania  donovani  (Ross),  is  found  in  closely  packed  masses  in  the 
cells  of  the  spleen  and  other  viscera.  These  organisms,  also  known  as 
Leishman-Donovan  bodies,  are  said  to  be  a  non-flagellate  stage  which 
develops  a  flagellate  stage  in  some  other  host.  They  are  "  ap- 
proximately circular  or  oval,  2.5  to  3.5  micra  in  diameter,  clearly  out- 
lined, and  appear  to  possess  a  distinct  cuticle,  as  they  retain  their  shape 
and  are  rarely  seen  distorted  in  films.  The  two  chromatin  masses 
are  characteristic,  the  large  one  staining  slightly  and  the  small  one  in- 
tensely with  Romanowsky.  The  masses  are  usually  situate  opposite 
each  other  in  the  short  axis  of  the  parasite." 

Observations  made  by  Patton  ^  show  that  flagellate  forms  develop 
in  from  five  to  eight  days  in  bedbugs  after  feeding  on  kala  azar  patients. 
Much  circumstantial  evidence  strongly  implicates  both  the  Indian  bed- 
bug Cimex  hemipterus  {C.  rotundatus  Patton)  and  the  common  Cimex 
lectularius  as  probable  important  transmitters  of  this  disease. 

Relapsing  Fever  (Spirochaetosis).  — ^  The  relapsing  fevers  traceable 
to  Spirochdta  duttoni  (African  form)  and  SpirochcBta  recurrentis 
(European  form)  are  probably  disseminated  to  some  extent  by  the 
bedbug  {Cimex  lectularius),  since  it  has  been  shown  by  Nuttall  ^  that 
the  spirochsetes  survive  in  the  bodies  of  bugs  for  a  period  of  six  days  at 
a  temperature  of  12°  C,  and  a  much  shorter  period  (six  hours)  at  20- 
24°  C.  He,  however,  succeeded  in  transmitting  the  disease  to  a  mouse, 
in  only  one  instance,  by  transferring  thirty-five  bugs  from  an  infected 
mouse  to  an  uninfected  mouse.  The  evidence  at  hand  seems  to  indicate 
that  the  bedbug  is  relatively  unimportant. 

Control.  —  The  habits  of  these  parasites  indicate  in  a  measure  the 
methods  useful  in  their  eradication  in  a  given  situation.  The  ease 
with  which  they  secrete  themselves  in  very  narrow  crevices  provides 
safety  against  anything  but  very  penetrating  materials.  Thus 
pyrethrum  powder  is  only  useful  where  the  insects  are  quite  exposed 
or  within  reach  of  a  blower.  The  newer  metal  bedsteads  are  easily 
kept  free  from  the  bugs,  while  the  old-fashioned  wooden  bedsteads  are 
more  difficult  to  handle;  however,  the  writer  has  seen  some  very  bad 
infestations  entirely  eliminated  by  the  use  of  kerosene  applied  by  means 
of  a  tail  feather  from  a  fowl.  The  more  penetrating  oils,  such  as  gasoline 
and  benzine  which  volatilize  more  readily,  are  to  be  recommended; 
however,  greater  precaution  against  ignition  must  he  exercised. 

A  thorough  infestation  of  bedbugs  will  require  a  more  strenuous 
campaign,  extending  even  to  the  removal  of  all  loose  wall  paper  under 
which  the  bugs  may  have  found  a  hiding  place.  Where  the  infestation 
has  reached  such  proportions  as  to  include  several  rooms  or  even 
an  entire  building,  the  more  rapid  and  effective  fumigation  methods 
are  far  preferable,  requiring  less  labor  and  producing  better  results. 

1  Patton,  W.  S.,  1907.     Sclent.  Mem.  of  the  Gov.  of  India.     Nos.  27  and  31 . 

2  Nuttall,  G.  F.  H.,  1913.  The  Herter  Lectures.  I.  Spirochaetosis.  Para- 
sitology, Vol.  5,  No.  4,  pp.  262-274. 


74  MEDICAL  AND   VETERINARY   ENTOMOLOGY 

Hydrocyanic  acid  gas  is  perhaps  the  most  effective  of  fumigating 
agents,  but  the  greatest  care  must  be  exercised  in  the  process, 
since  the  gas  is  deadly  to  all  forms  of  animal  life  and  extremely 
penetrating.  Rooms  above  apartments  in  which  this  gas  is  being 
applied  should  not  be  occupied  during  or  immediately  after  the  process. 
Sparrows  have  been  known  to  drop  from  the  eaves  of  houses  in  which 
cyanide  fumigation  was  going  on.  However,  with  proper  precautions 
very  little  danger  is  involved. 

To  prepare  a  room  for  cyanide  fumigation,  all  wet  or  moist  food- 
stuffs must  be  removed  (dry  materials  such  as  flour,  meal,  bread,  etc. 
need  not  be  removed) ;  if  the  house  is  occupied,  there  must  be  no  crevices 
leading  from,  the  room  to  be  fumigated  to  occupied  rooms.  It  is  best  that 
the  house  should  be  vacated  during  the  process,  —  this  need  be  for  only 
a  period  of  five  or  six  hours.  Fumigation  should  not  be  undertaken 
when  it  is  cold ;  a  temperature  of  about  70°  F.  gives  best  results.  If 
there  is  a  fireplace  in  the  room,  this  should  be  covered  with  a  blanket 
or  other  covering.  All  crevices,  such  as  occur  around  the  doors  and 
window  sashes,  keyholes,  etc.,  must  be  tightly  covered  with  strips  of 
paper  pasted  in  place  with  a  very  dilute  flour  paste,  or  as  some  have 
found,  merely  soaked  in  water.  The  cubic  contents  of  the  room  must 
be  estimated  and  sufficient  ingredients  provided  to  do  the  work.  One 
ounce  of  potassium  cyanide  for  every  one  hundred  cubic  feet  of  space  is 
necessary.  To  generate  the  gas  sulphuric  acid  and  water  must  be 
used.  The  following  proportions  are  needed  for  one  hundred  cubic 
feet  of  space :  — 

Potassium  cyanide  (98  %)       1  oz. 

Sulphuric  acid  (about  66°  Beaum^) 1  fluid  oz. 

Water 3  fluid  oz. 

or  for  130  cubic  feet  of  space  :  — 

Sodium  cyanide  (129  %) ■ 1  oz. 

Sulphuric  acid 1  fluid  oz. 

Water 2  fluid  oz. 

To  proceed  place  the  water  (in  proper  proportion)  in  a  heavy  two 
to  three  gallon  earthen  jar  placed  on  thick  folds  of  paper  to  catch 
spattered  liquid,  then  slowly  add  the  sulphuric  acid  (water  always  first, 
then  the  acid),  lastly  drop  a  paper  bag  containing  the  cyanide  into  the 
liquid,  holding  same  at  arm's  length,  and  immediately  beat  a  hasty  re- 
treat, carefully  closing  the  door.  After  the  expiration  of  about  five 
hours,  open  the  windows  from  the  outside  and  permit  the  room  to 
"air"  until  the  "peach  kernel"  odor  has  disappeared.  The  contents 
of  the  jar  should  be  carefully  disposed  of. 

In  treating  an  entire  building  the  operator  must  always  begin  at 
the  top  and  work  downward. 

To  fumigate  with  sulphur,  a  very  efficient  method  to  destroy  bed- 
bugs and  other  vermin,  flowers  of  sulphur  or  lump  sulphur  is  used.     The 


BEDBUGS  AND   CONE  NOSES  75 

rooms  are  prepared  as  for  hydrocyanic  acid  gas  fumigation.  All  metal 
objects  and  fine,  delicately  tinted  fabrics  must  be  removed,  if  possible ; 
metallic  objects  may  also  be  covered  carefully  or,  what  is  better,  coated 
with  vaseline.  Sulphur,  at  the  rate  of  four  pounds  to  every  1000  cubic 
feet  of  space,  is  placed  in  a  shallow  iron  pot  or  skillet  which  is  placed  on 
bricks  or  stones  in  a  tub  in  which  there  is  a  little  water  in  order  to  pre- 
vent spilling  out  and  igniting  the  floor.  The  sulphur  is  easily  ignited 
by  pouring  over  it  a  few  ounces  of  wood  alcohol  (or  grain  alcohol)  and 
then  lighting  it  with  a  match.  Fumigation  must  continue  for  at  least 
two  hours,  when  the  doors  and  windows  should  be  opened  to  ventilate 
the  room  before  occupancy. 

While  sulphur  fumes  (sulphur  dioxid)  are  extremely  useful  against 
insects  and  other  animal  life,  such  as  rats  and  mice,  the  liability  to  bleach 
fabrics  and  paper,  and  tarnish  metals  is  against  this  method  unless 
conditions  are  absolutely  dry. 

The  natural  enemies  of  the  bedbug,  such  as  red  ants  and  cockroaches, 
do  not  enter  in  as  practical  factors,  inasmuch  as  they  are  just  as  un- 
desirable as  the  bedbug  itself. 

Repellents  have  had  little  or  no  consideration ;  however,  old 
residents,  who  have  had  to  live  under  conditions  where  bedbugs  were 
plentiful,  e.g.  taverns  and  inns,  state  that  they  have  found  great  relief 
in  the  use  of  leaves  of  the  "  bay  tree  "  merely  placed  among  the 
bedding. 

B.     The  Cone-Noses 
Order  Hemiptera,  Family  ReduviidoB 

The  Reduviidae.  —  Members  of  the  family  Reduviidse  as  typical 
representatives  of  the  order  Hemiptera,  suborder  Heteroptera,  have  the 
basal  half  of  the  wing  covers  thick  and  leathery.  The  mouth  parts, 
(Fig,  26),  which  are  piercing  structures  jmr  excellence,  consist  of  a  three- 
jointed  proboscis  extending  from  the  extreme  distal  end  of  the  head, 
and  directed  backward  between  the  fore  coxse  while  at  rest.  The  rather 
cone-shaped  form  of  the  head  gives  rise  to  the  popular  term  "  cone-noses  " 
applied  to  certain  of  these  insects.  The  long,  slender,  four-segmented, 
naked  antennae  (basis  for  the  term  Gymnocerata)  are  located  in  front 
of  the  prominent  eyes  on  the  border  of  the  head.  The  Reduviidae  are 
predaceous  in  their  feeding  habits  to  a  marked  degree,  hence  the  term 
"assassin  bugs."  Creeping  slowly  toward  their  victims,  these  assassins 
suddenly  pounce  upon  the  unsuspecting  insect,  into  which  are  thrust  the 
strong,  sharp,  needle-like  stylets  and  the  juices  sucked  out.  The  victim 
is  ordinarily  another  insect;  however,  there  are  several  species  of  cone- 
noses  which  evidently  feed  on  mammalian  blood  if  the  opportunity  is 
offered. 

]Many  of  the  recorded  cases  of  cone-nose  bites  indicate  that  the 
"bite"    inflicted  was  not   "premeditated,"    but   quite   accidental   or 


76         MEDICAL  AND   VETERINARY  ENTOMOLOGY 

rather  an  act  of  self-defense.  The  writer's  first  experience  with  a 
cone-nose  was  while  incautiously  plucking  a  leaf  from  a  tree.  The 
bite  was  instant  and  the  pain  most  intense,  and  though  the  wound  was 
on  the  finger  the  pain  seemed  to  extend  to  the  head  and  was  followed  by 
a  feeling  of  faintness.  The  recovery,  however,  was  but  a  matter  of 
less  than  half  an  hour  with  no  after  effects  except  for  a  slight  local 
cellulitis. 

The  kissing  hug  scare  of  1899  was  traced  to  the  presence  of  what 
was  perhaps  an  unusual  abundance  of  Reduviidse  of  a  given  species, 
and  the  fact  that  individuals  were  commonly  bitten  about  the  lips  and 
face  gave  rise  to  the  above  popular  cognomen.  Many  of  these  bites  were 
pretty  surely  induced  by  grasping  the  insects  with  the  fingers  as  they 
flew  into  the  face  at  night.  The  common  kissing  bug  {Opsicoetes 
(Reduvius)  personatus)  is  strongly  positively  phototropic,  hence  dashes 
vigorously  at  a  light  and  often  into  the  face  of  any  one  near  by. 

Opsicoetes  (Reduvius)  personatus  Linn,  is  one  of  the  commoner  species 
of -Reduviids,  having  a  wide  distribution,  ranging  over  the  entire  eastern 
part  of  the  United  States  as  far  west  as  the  Rocky  Mountains.  It  is 
originally  a  European  form  and  has  now  become  well-nigh  cosmopolitan. 
This  insect  is  about  two  centimeters  in  length,  and  is  coal  black.  The 
prothorax  in  dorsal  aspect  has  two  prominent  tubercles  or  swellings, 
due  to  a  median,  dorsal,  longitudinal  groove  and  a  transverse  posterior 
groove.  The  young  present  a  very  curious  masked  appearance  because 
of  a  covering  of  lint  and  dust,  which  adheres  to  the  body  by  means  of 
a  sticky  secretion. 

This  species  is  commonly  known  as  the  "  kissing  bug  "  which  pro- 
vided much  "  story  "  material  for  the  newspapers  of  the  Eastern  states 
during  the  summer  of  1899.  It  inflicts  a  very  painful  wound.  Howard  ^ 
quoting  LeConte  writes :  "  This  species  is  remarkable  for  the  intense 
pain  caused  by  its  bite.  I  do  not  know  whether  it  ever  willingly 
plunges  its  rostrum  into  any  person,  but  when  caught  or  unskillfuUy 
handled  it  always  stings  (pierces).  In  this  case  the  pain  is  almost 
equal  to  that  of  the  bite  of  a  snake,  and  the  swelling  and  irritation  which 
result  from  it  will  sometimes  last  for  a  week.  In  very  weak  and  irri- 
table constitutions  it  may  even  prove  fatal." 

Conorhinus  sanguisuga  Lee.  is  known  as  the  "  blood-sucking  cone- 
nose,"  also  called  the  "  big  bedbug."  Conorhinus  is  probably  a  typical 
South  American  and  Mexican  genus,  but  this  species  is  commonly  found 
in  the  Southern  states  of  the  U.  S.,  occurring  as  far  north  as  southern 
Illinois  and  Ohio.  The  "  big  bedbug "  has  secured  this  name  for 
itself  because  of  its  frequent  presence  in  bedrooms  and  beds.  Since 
several  species  of  the  Reduviids  are  known  to  capture  and  feed  on  bed- 
bugs it  is  quite  likely  that  this  species  shares  this  habit,  probably  pre- 

Howard,  L.  0.,  1899.  The  Insects  to  whieh  the  name  "Kissing  Bugs" 
became  applied  during  the  summer  of  1899.  U.  S.  Dept.  of  Agric,  Div.  Ento. 
Bull.  No.  22. 


BEDBUGS  AND   CONE-NOSES 


77 


ferring  human  blood  second-hand,  but  will  just  as  soon  partake  of  this 
luxury  at  first  hand  if  the  opportunity  offers  itself. 

This  cone-nose  is  from  2  to  2^  cm.  in  length,  and  is  dark  brown  in 
color  with  pinkish  segmental  markings  on  the  dorsal  borders  of  the  ab- 
domen and  on  the  tips  and  bases  of  the  hemi-elytra.  In  other  respects 
it  is  a  typical  Reduviid  of  the  fiercest  appearance.  The  bite,  if  anything, 
is  even  more  severe  than  that  of  the  former  species  and  results  in  more 
uniform  symptoms.  Because  of  the  uniform  character  of  the  symptoms 
Marlatt  suggests  that  a  specific  poison  is  injected  into  the  wound. 
There  is  ordinarily  "  a  burning  pain,  intense  itching  and  much  swelling  " 
with  the  appearance  of  "  red  blotches  and  welts  all  over  the  body  and 
limbs."  The  effects  of  the  bite  may  last  for  months;  however,  they 
usually  disappear  within  a  few  days. 

Conorhinus  protractus  Uhler  (Fig.  67),  commonly  known  as  the 
"  China  bedbug,"  is  a  widely  distributed  Pacific  Coast  species  and  is 
responsible  for  the  large  majority 
of  cone-nose  bites  in  California, 
where  it  has  been  reported  from 
many  localities.  This  species  is 
frequently  found  indoors  and 
averages  18  mm.  in  length,  and  is 
nearly  dead  black  in  color  through- 
out. The  abdomen  is  broad  with 
a  wide  margin  exposed  around  the 
narrow  folded  wings  lying  in  the 
dorsal  concavity.  Van  Duzee  re- 
ports collecting  this  species  com- 
monly in  the  nests  of  wood  rats. 

The  symptoms  produced  by 
Conorhinus  protractus  are  ordi- 
narily described  by  local  physi- 
cians, viz. :  "  In  a  few  minutes 
after  a  bite  the  patient  develops 
nausea,  flushed  face,  palpitation 
of  the  heart,  rapid  breathing,  rapid  pulse,  followed  by  profuse  urticaria 
all  over  the  body.  The  symptoms  vary  with  individuals  in  their 
intensity."  Inquiries  with  regard  to  this  species  are  most  frequent 
during  May  and  early  June. 

Melanolestes  picipes  H.  S.  resembles  the  above  very  closely,  but  is 
more  slender  and  is  a  typical  field  species,  as  is  M.  abdominalis  H.  S. 
and  Apiomerus  crassipes  Fabr.,  the  latter  a  heavy-set,  pilose,  droll-looking 
creature,  —  all  of  these  inflict  painful  bites. 

Rasahas  higuttatus  Say,  the  "  two-spotted  corsair,"  is  quite  common  in 
the  Southern  states,  Cuba  and  South  America,  and,  according  to  Van 
Duzee,  giving  way  in  the  northwest  and  California  to  R.  thoracicus 
Stal  (Fig.  68),  a  very  closely  related  form.     The  writer  has  taken  this 


Fig.  67.  —  A  cone-nose,  Conorhinus  protrac- 
tus, also  known  as  the  China  bedbug.    X  2.1. 


78 


MEDICAL  AND    VETERINARY   ENTOMOLOGY 


Fig.  68.^ — The    "two-spotted    corsair,' 
Rasahus  biguttatus  var.  thoracicus.    X  2.1. 


latter  species  in  many  parts  of  California  from  the  Imperial  Valley  to 
the  Sacramento,  but  has  only  a  few  records  of  its  attacking  human 

beings,  though  Howard  ^  reports 
thus :  "  Dr.  x\.  Davidson,  formerly 
of  Los  Angeles,  in  an  important 
paper  entitled  'So-called  Spider  Bites 
and  their  Treatment  '  published  in 
the  Therapeutic  Gazette  of  February 
15,  1897,  arrives  at  the  conclusion 
that  almost  all  of  the  so-called  spider 
bites  met  with  in  southern  Cali- 
fornia are  produced  by  no  spider  at 
all  but  by  Rasahus  biguttatus.  The 
symptoms  which  he  describes  are  as 
follows :  Next  day  the  injured  part 
shows  a  local  cellulitis  with  a  dark 
central  spot ;  around  this  spot  there 
frequently  appears  a  bulbous  vesicle 
about  the  size  of  a  ten-cent  piece  and 
filled  with  a  dark  grumous  fluid ;  a 
smaller  ulcer  forms  underneath  the 
vesicle,  the  necrotic  area  being  generally  limited  to  the  central  part, 
while  the  surrounding  tissues  are  more  or  less  swollen  and  somewhat 
painful.  In  a  few  days  with  rest  and  proper  care  the  swelling  sub- 
sides, and  in  a  week  all  traces  of 
the  cellulitis  are  usually  gone.  On 
some  of  the  cases  no  vesicle  forms  at 
the  point  of  injury,  the  formation 
probably  depending  on  the  constitu- 
tional vitality  of  the  individual  or 
the  amount  of  poison  introduced." 
This  species  has  also  the  repu- 
tation of  being  a  bedbug  hunter. 

Life  History.  —  Though  the  life 
history  (Fig.  69)  of  but  a  very  few 
species  of  Reduviid  has  been  worked 
out  completely,  it  seems  likely  that 
all  the  species  mentioned  have  but 
one  generation  a  year.  The  eggs  of 
Conorhinus  sanguisuga  are  said  to  be 
white  at  first,  then  yellow,  and  finally  become  pinkish  in  color ;  they  are 
barrel-shaped  and  are  deposited  on  end,  the  compact  mass  of  twenty- 
five  to  thirty  forming  a  rather  regular  five  or  six  sided  figure.  The  young 
insects  emerge  in  about  twenty  days.  The  metamorphosis  is  simple. 
Conorhinus  protradus  deposits  its  large  white  eggs  (few  in  number) 
1  Howard,  L.  O.,  1899  {loc.  cit.). 


Fig.   69.  —  Egg  (left)  and  larva  (right),  of  a 
cone-nose,  Conorhinus  protractus.     X  4.4. 


.  BEDBUGS   AND   CONE-NOSES  79 

during  midsummer  and  these  hatch  ordinarily  in  about  three  weeks, 
the  first  molt  taking  place  in  seven  or  eight  days  after  hatching. 

Chagas  Disease  (Brazilian  Trypanosomiasis).  —  In  1909  Chagas  ^ 
reported  from  Brazil  an  endemic  human  trypanosomiasis.  This  disease 
occurs  in  its  acute  form  in  infants  and  in  its  chronic  form  in  adults. 
It  is  characterized  by  an  irregular  fever,  anaemia,  enlargement  of 
lymphatic  glands,  particularly  an  enlargement  of  the  thyroid.  The 
causative  organism  Schizotrypanum  cruzi  Chagas  is  said  to  be  present 
in  the  peripheral  blood  of  children  during  the  fever,  but  in  adults  and 
children  during  later  periods  occurs  in  the  cells  of  the  thyroid,  bone 
marrow  and  other  tissues,  resembling  Leishmania  during  its  segmenta- 
tion stage.  The  flagellate  form  is  said  to  enter  the  lungs  of  the  host, 
where  the  flagellum  is  lost  and  an  oval  form  is  taken  on. 

Chagas  found  theprotozoonin  the  intestine  of  a  cone-nose,  Conorhinus 
megistus  Burm.  (also  referred  to  the  genus  Triatoma),  and  succeeded  in 
transmitting  it  through  the  cone-nose  to  rodents.  As  reported,  the  in- 
cubation period  (after  the  bite)  varies  from  ten  to  fourteen  days. 

There  is  some  difference  of  opinion  as  to  mode  of  transmission ; 
Chagas  evidently  believing  that  the  parasites  multiply  in  the  intestine 
of  the  cone-nose,  passing  thence  to  the  salivary  glands,  infection  taking 
place  directly  with  the  bite.  Brumpt,^  on  the  other  hand,  says  that 
infection  results  through  the  infective  dejecta  of  the  insect  deposited 
upon  the  skin  of  the  host  when  the  insect  bites,  inoculation  taking 
place  through  the  mucous  membrane  of  the  mouth,  inasmuch  as  the 
cone-nose  usually  bites  the  face  and  lips  of  sleeping  persons. 

Control.  —  The  conspicuous  size  of  these  insects  should  make  it  an  easy 
matter  to  find  them  in  bedrooms,  when  it  is  known  that  they  are  common. 

Since  they  are  attracted  by  light  at  night,  it  is  wise  to  screen  windows 
and  doors.  Considerable  precaution  should  be  exercised  when  a  speci- 
men has  alighted  on  the  face  or  hands ;  do  not  grasp  it  between  the 
fingers,  this  will  pretty  surely  cause  the  insect  to  thrust  its  proboscis 
at  once  into  the  flesh.  A  quick  snap  of  the  finger  will  generally  re- 
move the  intruder  without  any  bad  results,  and  the  insect  can  then  be 
crushed.     They  are,  how^ever,  rapid  in  their  movements. 

Treatment  for  the  Bite.  —  Treatment  for  the  bite  of  cone-noses 
has  usually  a  twofold  object;  first,  to  neutralize  the  specific  poison  of 
the  cone-nose,  and  secondly,  to  prevent  extra  infection  which  is  liable 
to  occur  because  of  the  indiscriminate  feeding  habits  of  the  insect. 
Bathing  the  wound  with  corrosive  sublimate  in  proportions  of  1  to  1000 
is  said  to  give  good  results,  as  will  also  ammonia. 

1  Chagas,  C,  1909.  Ueber  eine  neue  Trypanosomiasis  des  Menschen. 
Memorias  do  Institute  Oswaldo  Cruz,  I,  pp.  159-218. 

2  Brumpt,  E.,  1913.  Immunite  partielle  dans  les  infections  a  Trypanosoma 
cruzi  transmission  de  ee  trypanosome  par  Cimex  rotundatus.  Role  regulateur 
des  botes  intermediaires.  Passage  a  travers  la  peau.  Bull.  Soe.  Path.  Exot., 
Vol.  VI,  No.  3,  pp.  172-176.  (Abstract  in  the  Review  of  Applied  Ento.,  Ser.  D., 
Vol.  I,  No.  7.) 


CHAPTER   IX 

MOSQUITOES 

Order  Diptera,  Family  Culicidce 

General  Characteristics.  —  As  members  of  the  Order  Diptera, 
mosquitoes  partake  of  the  general  characters  of  the  order;  namely, 
reduction  of  the  metathoracic  (posterior)  pair  of  wings,  in  place  of  which 


Fig.  70.- 


-  Crane  fly  (Tipula),  often  mistaken  for  a  mosquito.     Hal  teres  visible 
immediately  behind  the  wings.       X  1. 


there  occurs  a  pair  of  tiny  knobbed  organs  known  as  the  halteres  or 
balancers,  most  distinctly  visible  in  the  crane  flies  (Tipulidfe)  (Fig.  70). 
The  Diptera  are  commonly  divided  into  two  suborders,  —  first, 
Nematocera,  in  which  the  antennae  are  many-jointed  and  filamentous, 

80 


MOSQUITOES 


81 


as  in  the  mosquitoes  (Culicidae),  crane  flies  (Tipulidse),  midges 
(Chironomidse)  and  buffalo  gnats  (Simuliidse) ;  secondly,  the  Brachy- 
cera,  in  which  the  antenna  are  short  and  not  thread-like,  as  in  the 
horseflies  (Tabanidae),  house  flies  (Muscidae)  and  botflies  (CEstridfe). 

The  CuHcidse  (mosquitoes)  are  distinguished  from  all  other  Nema- 
toceran  Diptera  by  (1)  the  character  of  the  wing  venation  (Fig.  71), 
which  varies  also  specifically  within  the  family ;  (2)  by  the  presence  of 
characteristic  scales  fringing  the  wings  and  more  or  less  abundant  on 
the  body  and  head  (Fig.  78).     The  family  may  be  divided  into  two 


">v  ■^■^»v:"^ 


■''''W',?,M\v'r 


humef^l  cross  vcm  auxLlijiru  vein  p«t\o\e  ol  X"-'' ma-rgl nil  cell 

il    cell  •,  '.         — !-/-^=.J-i-"  ^^-a..^  _.■■        J       .     , 

4-*^  yein 
vein 
-S'-^ve'in 
S^^  vein 

Fig.  71.  —  Showing  (upper  figure)  scaly  wing  of  a  mosquito  with  spots  of  Anopheles; 
(lower  figure)  wing  venation  of  a  mosquito  with  veins  and  cells  named  and  numbered 
for  systematic  purposes.       X  23. 

divisions :  the  Corethrinse  or  short-beaked,  non-blood-sucking  mosquitoes, 
represented  by  the  genus  Corethra  (Fig.  72),  and  the  Culicinae  or 
long-beaked,  blood-sucking  true  mosquitoes.  The.  males  of  all  mos- 
quitoes are  non-blood-sucking. 

Nearest  Allies.  —  There  are  many  Dipterous  insects  which  may  be 
easily  mistaken  for  mosquitoes  unless  a  careful  microscopical  examina- 
tion is  made.  For  all  practical  purposes  the  characteristics  referred 
to  above  should  serve  to  determine  whether  the  insect  in  hand  is  a 
mosquito  or  not.  It  is  true  that  other  families  of  Diptera  are  in  some 
cases  provided  with  scales,  but  other  simple  characters  to  be  pointed 
out  here  should  serve  to  eliminate  these.  The  most  commonly  mistaken 
insects  are  members  of  the  family  Chironomidse,  the  midges  (Fig.  73). 
According  to  Williston  these  may  be  distinguished  from  mosquitoes  in 
that  the  costal  vein  is  not  continuous  on  the  posterior  side  of  the  wing. 


82 


MEDICAL  AND   VETERINARY   ENTOMOLOGY 


The  wings  are  usually  bare  or  in  some  may  be  hairy.  The  proboscis 
is  short,  and  in  all  except  the  "  punkies  "  or  "  no-see-ums  "  are  non- 
blood-sucking.  These  latter  are  tiny  gnats,  but  vicious  biters.  The 
most  common  Chironomids  which  often  occur  in  enormous  swarms  over 
or  near  swamps  have  bare  wings,  plumose  antenna"  and  do  not  bite. 

In  size  and  general 
form  they  resemble 
mosquitoes  very 
closely,  particularly 
male  mosquitoes. 

Members  of  the 
family  Tipulidse,  crane 
flies  or  "  daddy  long- 
legs  "  are  commonly 
mistaken  for  mosqui- 
toes. The  commoner 
species  are  usually  dis- 
tinguished by  the  pres- 
ence of  a  V-shaped 
suture  situated  dorsally 
on  the  thorax  (mesono- 
tum)  (Fig.  74)  and  by 
the  blunt,  non-piercing 
mouth  parts.  The 
wings  are  usually 
devoid  of  scales  or 
hairs  (some exceptions). 
Other  mosquito-like 
Diptera  are  the  Dixa 
midges  (Fam.  Dixidse), 
in  which  the  mouth 
parts  are  blunt  and  the 
wing  veins  are  devoid 
of  scales;  the  family 
Psychodidse  includes 
the  moth-like  flies 
which  are  densely  cov- 
ered with  hairs  and  are 
not  easily  mistaken  for 
mosquitoes  The  "  papatici  flies,"  members  of  this  family  and  of  the 
genus  Phelebotomus,  are  blood-sucking  and  occur  in  the  Philippine 
Islands,  parts  of  Asia,  Africa  and  South  America. 

Life  History.  —  A  general  statement  of  life  history  as  applied  to 
mosquitoes  is  not  possible  if  the  time  required  for  complete  transforma- 
tion is  desired,  inasmuch  as  this  varies  considerably  for  the  genera  and 
even  for  species.     However,  it  may  be  said  with  certainty  that  all  mos- 


FiG.  72.  —  Corethra,  easily  mistaken  for  a  mosquito,  is  an 
insect  belonging  to  the  family  Culicidse  (note  scaly 
wings)  but  is  non-blood-sucking.  (After  Smith.) 
X  12. 


MOSQUITOES 


83 


quitoes  pass  through  a  complex  metamorphosis  represented  by  the  usual 
stages,  egg,  larva,  i')n'pa  and  imago  {Y\g.  75).  The  larvfie  are  commonly 
called  "  wrigglers  "  and  the  pupa?  "  tumblers."  Water  in  which  to 
pass  the  larval  and  pupal  stages  is  absolutely  essential.  The  eggs  may 
be  deposited  on  wet  mud  and  the  larvee  may  exist  for  some  hours  in 
similar  situations.  With  reference  to  this  How^ard  states  that  "  In 
no  case,  however,  were  we  able  to  revive  larvje  in  mud  from  which  the 
water  had  been  drawn  off  for  more  than  forty-eight  hours,  and  after 
twenty-four  hours  only  a 
small  proportion  of  the 
larvae  revived." 

The  eggs  of  mosqui- 
toes are  deposited  from 
early  spring  to  early 
autumn,  and  in  warmer 
parts  active  "  wrigglers  " 
may  be  found  through- 
out the  year.  The  writer 
has  found  nearly  full- 
grown  larva?  in  parts  of 
California  in  January  and 
pupse  from  which  occa- 
sional imagines  emerged 
during  the  month  of 
February.  These  over- 
wintering larvae  are  quite 
certainly  from  eggs  de- 
posited late  in  the  autumn 
and  in  which  growth  is 
very  slow.  Mosquitoes 
which  make  their  appear- 
ance early  in  the  spring 
are,  as  a  rule,  individuals 
which  have  been  in  hiber- 
nation during  the  winter. 

Probably  about  ten 
days  is  the  shortest  time 

for  any  of  the  commoner  species  of  mosquitoes  to  pass  through  the 
various  developmental  stages  ;  Howard  gives  the  time  for  Culex  pungens 
as  "  sixteen  to  twenty-four  hours  for  the  egg,  seven  days  for  the  larvae, 
and  two  days  for  the  pupa."  From  this  rather  short  life-history  period 
the  time  required  to  pass  through  the  same  transformation  may  be  two 
or  three  weeks,  and  under  lower  temperature  conditions,  several  months. 
At  a  maintained  temperature  of  24°  ±  1°  C.  Cidiseta  incidens  required 
about  twenty -four  hours  for  the  eggs  to  hatch,  the  larvae  molted  on  the 
fourth  day  after  hatching  and  again  on  the  eighth  day,  pupating  on  the 


Fig. 


73. — A  midge   (ChironomicUe),  often  mistaken 
for  a  mo.squito.      (After  Osborn.)       X  12. 


84  MEDICAL  AND   VETERINARY   ENTOMOLOGY 

eleventh  day,  thus  giving  about  ten  days  for  the  larval  period;  mos- 
quitoes emerged  on  the  second  day  after  pupation,  requiring  about 
thirty-six  hours  for  this  stage.  The  mosquitoes  were  given  a  suck  of 
blood  within  twenty-four  hours  and  in  four  days  thereafter  deposited 
eggs.  This  gives  a  period  of  about  eighteen  days  from  egg  to  egg  under 
favorable  conditions. 


Fig.  74.  —  Head  and  thorax  of  a  crane  fly  (Tipulidae),  showing  appendages,  hal teres 
(h)  and  characteristic  v-shaped  suture  on  thorax  (v). 

The  longevity  of  the  female  mosquito  is  a  matter  not  so  easily  deter- 
mined because  of  the  conditions  needed  in  ascertaining  this ;  outdoor 
observations  naturally  offer  a  great  handicap  to  the  observer.  By 
feeding  mosquitoes  on  ripe  banana  and  blood,  it  has  been  possible  to 
keep  them  in  captivity  as  long  as  two  months,  but  this  is  probably 
longer  than  the  average,  because  by  far  the  greater  number  of  females 
die  in  captivity  within  two  or  three  weeks,  while  the  males  only  live 
three  or  four  days.  It  should  be  remembered,  of  course,  that  mosquitoes 
in  hibernation  may  live  as  long  as  six  or  seven  months.  It  is  quite 
probable  that  the  average  active  lifetime  of  the  female  mosquito  under 
natural  conditions  will  be  found  to  be  pretty  close  to  thirty  days,  as  the 
writer  has  observed  for  several  species  of  Sarcophagid  and  Muscid  flies. 

Internal  Anatomy.  —  To  be  prepared  to  study  the  relation  of  mos- 
quitoes to  such  diseases  as  malaria  and  filariasis  the  student  must  be 
familiar  with  their  internal  anatomy,  which  offers  specializations  of 
importance. 


MOSQUITOES 


85 


The  alimentary  canal  is  separable  into  three  regions,  the  fore-, 
mid-  and  hind-gut,  each  of  which  is  again  subdivided  into  more  or  less 
distinct  divisions  (Fig.  76).     Thus  the  fore-gut  consists  of  the  sucking 


¥ 


Fig.  75.  — ■Illustrating  the  life  history  of  a  mosquito  {Anopheles  quadriinaculatus) .     a.  egg  ; 
b.  larva  or  wriggler  (viewed  from  above)  ;    c.  pupa  or  tumbler ;    d.  adult.       X  5. 

tube  of  the  proboscis,  the  pharynx,  including  pumping  organ  and  the 
esophagus  with  its  diverticulae  (two  or  three  in  number  and  known  as 
food  reservoirs) ;    the  mid-gut  consists  of  a  narrower  anterior  portion 


Fig.  76.  —  Internal  anatomy  (in  part)  of  a  mosquito,  a.  head;  h.  thorax;  c.  abdomen; 
ant.,  antenna;  pip.,  palpus  ;  prb.,  proboscis  ;  hr.,  brain;  sbbt.,  subesophageal  ganglion; 
nch.,  ventral  nerve  chord  ;  ph.,  pharynx  ;  oes.,  esophagus  ;  res.,  food  reservoir,  of  which 
there  are  three  (esophageal  diverticula)  ;  prov.,  proventriculus  (false)  ;  st.,  stomach  or 
mid-gut ;  il.,  ileum  ;  col.,  colon  ;  reel.,  rectum  ;  mpgt.,  Malpighian  tubules  ;  sal.,  salivary 
gland  ;  salvsvr.,  salivary  reservoir  ;  said.,  salivary  duct.  (Adapted  after  various 
authors  and  based  on  dissections.) 

(false  proventriculus)  and  a  wdder  posterior  portion  (stomach)  occupying 
the  thorax  and  much  of  the  abdomen,  and  limited  posteriorly  by  the 
origin  of  the  five  Malpighian  tubules  which  indicate  the  beginning  of  the 
viscera  or  hind-gut ;  the  hind-gut  is  bent  on  itself  several  times  and 
consists  of  the  narrow,  longer  ileum,  the  colon  and  what  is  arbitrarily 
termed  rectum  marked  anteriorly  by  a  slight  constriction. 


86         MEDICAL  AND   VETERINARY  ENTOMOLOGY 

The  salivary  system  consists  of  two  sets  of  salivary  glands  (right  and 
left),  three  glands  to  each  set  (Fig.  76).  These  organs  are  situated 
ventrally  in  the  thorax  near  the  neck.  Each  set  of  glands  empties  into 
a  duct  which  combines  with  the  opposite  one  to  form  the  common 
salivary  duct.  This  common  duct  empties  its  contents  into  the 
esophagus  through  the  salivary  receptacle  close  to  the  base  of  the 
proboscis. 

The  reproductive  system  of  the  female  mosquito  occupies  the  posterior 
portion  of  the  abdomen  and  comprises  a  pair  of  ovaries  joined  by  a  pair 
of  oviducts  terminating  in  the  vagina  and  ovipositors,  one  to  three 
(depending  on  the  species) ;  spermathecw  are  present.  The  spermathecse 
of  an  impregnated  female  contain  myriads  of  spermatozoa,  and  the 
ovaries  when  mature  occupy  the  larger  part  of  the  abdomen. 


■f 

1 

1 

\ 

1 

y          \ 

l1 

h 

c 

Fig.  77.  —  Heads  of  mosquitoes,  showing  relative  length  of  palpi.  Useful  in  distinguish- 
ing the  two  main  subdivisions  of  mosquitoes,  a.  Culicine ;  b.  male  of  either  group ; 
c.  Anopheline. 

Sexual  Differences.  —  The  males  of  many  species  of  mosquitoes  are 
provided  with  plumose  antennae  (Fig.  77)  ;  in  the  female,  as  a  rule, 
these  organs  are  slender,  thread-like  and  covered  with  short  lateral 
hairs.  In  the  males  the  palpi  are  with  few  exceptions  long  (as  long  or 
longer  than  the  beak),  conspicuous,  jointed  organs  and  quite  hairy  (Fig. 
776).  In  the  iEdina  the  palpi  are  short  in  both  sexes.  Inasmuch  as 
males  do  not  feed  on  blood  they  are  less  frequently  found  about  human 
habitations.  Sweeping  with  the  insect  net  in  grass  or  other  low  vege- 
tation will  usually  result  in  the  capture  of  males  if  there  is  a  breeding 
place  near  and  it  is  the  proper  season. 

Characters  of  Systematic  Value.  —  Although  most  authors  have 
discarded  the  relative  length  of  palpi  as  a  useful  character  in  separating 
the  Culicinffi  into  three  divisions  or  tribes,  we  still  find  this  very  useful, 
particularly  in  localities  where  malaria  control  work  is  in  progress.  On 
this  basis  the  tribe  Culicini  includes  mosquitoes  in  which  the  palpi  of 
the  females  are  less  than  half  as  long  as  the  proboscis  (Fig.  77a) ;  the 
tribe  Anophelini  includes  mosquitoes  in  which  the  palpi  of  the  females 


MOSQUITOES 


87 


proboscis  (Fig.  77c).  The  males  of 
as  long  as  or  longer  than  the  probos- 
designated  the  .^dini,  in  which  the 


are  nearly  or  quite  as  long  as  the 
both  tribes  are  provided  with  palpi 
cis,  except  in  what  were  formerly 
palpi  of  both  males  and  females 
are  short ;  the  palpi  are  com- 
monly quite  hairy,  as  are  the 
antennje  (Fig.  776). 

The  determination  of  the 
genera  and  species  by  some 
authors  is  based  quite  largely 
on  the  character  of  the  scales. 
The  scales  on  the  head  and 
body  are  of  several  varieties,  as 
shown  in  Fig.  78.  The  occur- 
rence and  arrangement  of  these 
scales  on  the  head,  thorax,  ab- 
domen and  wings  provides  a 
basis  for  distinguishing  the 
genera,  as  illustrated  by  Fig. 
79.  Stephens  and  Christophers 
state,  "  All  mosquitoes  belong- 
ing to  the  genus  Culex  have  on  the  head  (1)  narrow  curved  and 
(2)  upright  forked,  but  only  (3)  a  few  flat  scales  laterally ;  whereas  all 


Fig.  78.  —  Varieties  of  Culicid  scales,  a,  b,  c, 
head  scales,  (a)  narrow  curved,  {h)  upright 
forked,  (c)  flat;  d-h,  thoracic  scales.  (Re- 
drawn after  Stephens  and  Christophers.) 


Fig.  79.  —  Occurrence  and  arrangement  of  scales  on  the  heads  of  mosquitoes,  (a) 
Stegomyia  ;  (6)  Anopheles  ;  (c)  Culex.  (Redrawn  in  part  after  Stephens  and  Chris- 
tophers.) 

mosquitoes  belonging  to  the  genus  Stegomyia  have  on  the  head  (1)  no 
narrow  curved  scales,  (2)  a  few  upright  forked  and  (3)  flat  scales,  cover- 
ing the  whole  of  the  head."  In  Anopheles  there  are  "  upright  forked 
scales  only  on  the  head." 


88 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


The  ungues  or  tarsal  claws  are  also  useful  characters  in  local  classifi- 
cation. In  some  species  the  claws  are  not  toothed  and  in  others  the 
claws  are  toothed. 

The  spotting  of  the  wings  is  not  a  safe  character  to  separate  the 
Culicini  from  the  Anophelini,  although  all  except  two  or  three  species  of 
Culicines  have  unspotted  wings,  and  all  but  one  or  two  Anopheline 
species  have  spotted  wings.  Culiseta  (Theobaldia)  incidens,  a  very 
common  Culicine  mosquito  of  California  and  elsewhere,  has  con- 
spicuously spotted  wings. 


Anopheline  Mosquitoes 

Adults. — As  already  stated,  the  Anophelini  are  roughly  distinguished 
from  the  Culicini  by  the  presence  of  long  palpi  in  both  males  and  females 

(Fig.   77).     The   proboscis   is   always 
straight  and  the  scutellum  is  simple, 
never  trilobed  (Stephens  and  Christo- 
phers).     The    commoner    Anopheline 
species  of  North  America  have  also  a 
characteristic  resting  attitude  (Fig.  80), 
i.e.  the  body  is  usually  thrown  up  at 
an  angle  with  the  surface  upon  which 
the  insect  is  resting ;  this  angle  is  the 
greatest  when  the  individual  is  resting 
on    the  ceiling,   for    the    reason   that 
gravity  acts  then  more  strongly  on  the 
heavy  abdomen.     When  resting  on  a 
table    or    other    horizontal    surface,    this 
angle  is  not  so  noticeable,  but  in  all  cases 
the  proboscis  is  nearly  or  quite  on  a  line 
with  the  body,  whereas  in  the  Culicini  the 
beak  and  body  form  a  distinct  angle. 

The  hum  of  Anopheles  is  all  but  in-"^ 
audible ;  where  the  Culicine  mosquito 
produces  a  high-pitched,  tantalizing  tone 
and  is  quickly  brushed  away,  the  Anoph- 
eles may  alight  and  actually  proceed  to 
pierce  the  skin  of  the  victim  before  it  is  ' 
detected. 

Anopheline  female  de- 
to  150  ova,  while  the 
a  larger  number,  often 
from  250  to  450.  In  the  former  case 
(including  ^Edes  (Stegomyia)  calopus  and 
other  iEdini)  the  individual  eggs  lie  flat 
on  the  surface  of  the  water  and  often  form 


Fig.  80.  —  Characteristic  atti- 
tude of  adult  mosquitoes  at 
rest.  a.  Anopheles  with  body 
normally  at  an  angle  of  from 
25°  to  55°  with  the  surface  ;  b. 
Culex,  with  body  parallel.    X  8. 


Eggs.  —  The 
posits  from  75 
Culicini   deposit 


MOSQUITOES 


89 


geometrical  figures  with  each  other,  owing  to  their  peculiar  form;  in 
the  latter  (Culicini)  (excepting  .-Edes  (Stegomyia)  calopus  and  other 
iEdini)  the  eggs  are  placed  on  end,  forming  a  boat-shaped  pack  or  raft 
(Fig.  81). 

On  examination  it  will  be  seen  that  the  individual   canoe-shaped 
Anopheline  egg  is  provided  on  the  upper  surface  with  a  pair  of  floats 


Fig.  81.  —  Mosquito  eggs,    (a)  egg  rafts  of  Culicine 
(6)  egg  masses  of  Anopheline.      (After  Howard.) 


^\0 


midway  on  either  side  and  with  cor- 
rugated edges  extending  nearly  the 
length  of  the  egg  (Fig.  82a).  The  in- 
dividual Culex  egg  tapers  decidedly  at 
the  upper  end  and  terminates  at  the 
base  in  a  globular  organ  called  the  "  micropilar  apparatus"  (Fig.  826). 
Larvae.  —  The  larvae  of  Culicine  mosquitoes  (Fig.  83a)  are  always 
suspended  from  the  surface  of  the  water  at  a  decided  angle  with  only 
one  portion,  the  anal  siphon, 
touching  and  penetrating  the  film, 
while  in  Anophelinse  (Fig.  836) 
the  larvse  lie  horizontal  with  at 
least  several  body  segments  com- 
ing dorsally  in  contact  with  the 
film.  At  the  point  of  contact  each 
segment  is  provided  with  a  group 
of  hairs  arranged  fanlike.  The 
eighth  abdominal  segment  in  both 
groups  is  provided  with  a  special- 
ized organ  through  which  the 
tracheae  (breathing  organs)  come 
in  contact  with  the  outer  air.  In 
the  Culicini  this  apparatus  is  pro- 
longed into  a  definite  breathing 
tube  (siphon),  while  in  the  Anophelini  this  tube  is  absent,  or  only 
slightly  protuberant  and  not  chitinous  as  in  the  former  (Fig.  83). 
So  abundant  are  the  wrigglers  at  times  that  a  small  pool  may  be 
literally  black  with  them.  Dr.  J.  B.  Smith  made  some  observations 
with  reference  to  numbers  in  AnopJieles  crucians  and  found   that  a 


Fig.  82.  —  Individual  mosquito  eggs.  (a) 
Anopheles ;  {h)  Culex ;  (c)  Stegomyia. 
(Adapted  after  Mitchell.) 


90 


MEDICAL  AND   VETERINARY   ENTOMOLOGY 


pond  with  an  area  of  1894  square  feet  contained  10,636,700  wrigglers, 
roughly  ten  and  one  half  millions,  or  5616  to  every  foot  of  area. 

The  movements  of  Anopheline  larvae  are  very  much  more  jerky 
than  those  of  the  Culicine,  in  which  the  wriggling  motion  is  worm-like. 
The  former  are  also  not  so  easily  seen  as  are  the  latter,  probably  owing 
to  their  horizontal  position  at  the  surface  of  the  water.  On  wading 
into  a  swamp  no  larvse  may  be  visible,  but  on  looking  backward  into 
the  now  muddy  water,  the  larvae  may  be  plainly  seen,  distinctly  out- 
lined against  the  murky  background. 

A  close  examination  of  the  feeding  Anopheline  larvae  will  show  that 
the  head  is  turned  dorsally  and  that  the  smaller  organisms  (animal  and 


Fig.  83.  —  Mosquito  larvae  in  natural  position 
in  the  water,  (a)  Culicine ;  (6)  Anopheline. 
X6. 

vegetable)  near  the  surface  form  the 
main  objects  of  diet.  The  Culicine 
larvae  usually  feed  on  organisms 
located  at  the  bottom  of  shallow  pools  and  at  the  sides  of  vessels,  etc. 

Pupae.  —  The  pupae  or  nymphs  of  all  mosquitoes  are  very  similar. 
In  all  cases,  instead  of  the  single  posterior  breathing  apparatus  of  the 
larva,  there  are  present  a  pair  of  breathing  trumpets  (right  and  left) 
located  on  the  thorax,  i.e.  anteriorly.  The  position  of  these  trumpets 
in  the  two  general  groups  of  mosquitoes  is  different  and  fairly  distinctive, 
i.e.  they  are  located  farther  forward  on  the  thorax  in  Anophelini,  near 
the  middle,  and  open  broadly  in  this  group,  being  more  slender  and 
relatively  longer  in  the  Culicini. 

In  position  the  two  groups  also  differ  somewhat,  i.e.  the  Anopheline 
pupae  hang  more  horizontally,  and  the  heavier  "head-end"  is  relatively 
longer. 

Life  History.  —  As  in  all  other  mosquitoes  and  insects  in  general  the 
life  history  depends  greatly  on  temperature.  In  early  spring  and  late 
autumn  the  development  is  retarded,  owing  to  the  lower  average  tempera- 
ture. 

In  midsummer  the  egg  stage  is  rarely  longer  than  twenty-four 
hours  and  often  nearer  twelve  hours  duration.  The  larva  emerges  by 
splitting  the  egg  (Fig.  84)    (or  in  the  Culicini  by  pushing  the  bottom 


MOSQUITOES 


91 


from  the  egg)  and  begins  its  existence  in  the  water,  usually  clinging 
close  to  debris  or  scum.  The  larval  stage  is  most  easily  affected  by 
temperature,  but  lasts  usually  from  twelve  to  fifteen  days,  during  which 
time  the  skin  is  shed  several  times.  The  change  into  the  nymphal  or 
pupal  stage  is  undergone  very  rapidly  and  usually  occurs  overnight; 


''     ■ 

* 

• 

Jk 

■S.J 

-        -V 

t                                                      -      V         ' 

fum 

1 

m 

//I 

^^^r 

/    /   . 

Fig.  84.  — Anopheles  mosquito  larva  just  emerged  from  the  egg.      X  50. 

great  numbers  may  undergo  this  change  in  the  early  part  of  the  night 
between  nine  o'clock  and  midnight.  This  stage  is  comparatively  short, 
requiring  seldom  over  thirty-six  hours.  At  the  end  of  this  time  the 
pupal  skin  bursts  along  the  mid-dorsal  side,  the  pupa  in  the  meantime 
having  straightened  out.  In  a  few  minutes  the  adult  has  pulled  itself 
out  of  the  pupal  skin,  and  quietly  balancing  itself,  remains  on  top  of  its 
cast  skin  until  its  wings  are  sufficiently  dry  to  permit  it  to  fly  away.  Thus 
it  must  be  inferred  that  the  process  of  emerging  requires  a  very  quiet 
body  of  water,  otherwise  the  mosquito  would  be  submerged  and  perish. 
Duration  of  Adult  Life.  —  As  a  rule  the  newly  emerged  females  will 
suck  blood  after  a  period  of  about  tw^enty-four  hours.  Numerous  ex- 
periments tried  on  the  male  mosquito  as  well  as  extensive  field  observa- 
tions seem  to  give  conclusive  evidence  that  this  sex  does  not  possess 
the  blood-sucking  habit,  living  exclusively  on  the  juices  of  plants  and 
"  plain  "  water.     However  well  one  may  care  for  the  males  they  in- 


92         MEDICAL  AND   VETERINARY  ENTOMOLOGY 

variably  die  within  a  week,  usually  in  about  three  days,  and  it  is  quite 
probable  that  very  little  nourishment  is  taken  during  this  time. 

In  captivity  the  mosquito  mortality  is  very  high,  and  it  is  therefore 
not  a  satisfactory  plan  to  estimate  the  average  length  of  life  on  the 
basis  of  laboratory  observations.  Basing  an  estimate  on  the  relative 
abundance  of  Anopheline  mosquitoes  in  a  given  district  during  several 
weeks  after  careful  control  measures  are  inaugurated,  it  seems  safe 
to  say  that  the  average  life  of  the  adult  female  mosquito  is  between  thirty 
and  forty  days,  perhaps  nearer  thirty.  This  does  not,  of  course,  refer 
to  hibernation.  Ordinarily  the  female  mosquito  dies  shortly  after  she 
has  deposited  her  eggs. 

Flight.  —  It  is  a  matter  of  common  observation  that  Anopheline 
mosquitoes  are  not  strong  fliers.  If  Anopheles  are  found,  one  can 
rest  assured  that  their  breeding  place  is  somewhere  very  near,  usually 
within  two  hundred  yards.  They  are  seldom  found  over  a  mile  away. 
However,  if  the  breeding  place  of  these  insects  is  connected  with  human 
habitations  by  means  of  low  herbage  at  close  intervals,  this  will  afford 
a  ready  means  of  advance.  On  the  other  hand,  it  seems  that  a  belt  of 
trees  tends  to  act  as  a  barrier. 

Unlike  certain  other  species  of  mosquitoes,  notably  salt-marsh  mos- 
quitoes, the  Anopheles  are  not  readily  carried  by  the  wind,  inasmuch  as 
they  take  to  cover  even  in  a  moderate  breeze  and  cling  to  vegetation. 

Hibernation.  —  The  writer  has  been  bitten  by  Anopheles  mosquitoes 
in  California  as  early  as  February  12,  and  at  noonday  at  that,  and  a 
specimen  w^as  captured  in  the  act  of  flying  about  in  a  church  on  the  first 
of  January.  Since  all  breeding  had  ceased  in  late  October,  it  must  be 
assumed  that  these  were  hibernated  individuals  which  had  been  induced 
to  leave  their  shelters  by  the  appearance  of  balmy  days.  In  the  colder 
Eastern  states  there  are  no  winter  days  when  it  is  balmy  enough  to 
induce  mosquitoes  to  come  forth  from  their  places  of  hibernation. 

The  first  case  mentioned  was  a  normal  response  to  the  usual  early 
spring  days  in  California,  where  breeding  begins  correspondingly  early. 
The  day  before,  i.e.  February  11,  mosquitoes  were  seen  emerging  from  be- 
neath a  schoolhouse  which  had  afforded  a  place  of  hibernation  during  the 
heavy  rains.     This  place  had  probably  been  sought  early  in  November. 

The  above  and  other  similar  experiences  afford  ample  evidence  that 
Anopheles  mosquitoes  which  have  been  in  hibernation  are  active  on 
emerging  even  by  daylight  (noonday)  and  bite  fiercely  during  that  time. 

Yellow  Fever  Mosquitoes 

Adults.  —  Mosquitoes  belonging  to  what  was  formerly  known  as 
the  genus  Stegomyia  (now  .-Edes),  of  which  there  were  twenty  or  more 
species,  are  all  beautifully  marked  with  silvery  white  or  yellowish  white 
bands  and  stripes  on  a  nearly  black  background,  whence  the  name 
."  tiger  mosquitoes  "  applied  to  the  members  of  this  group. 


MOSQUITOES 


93 


94 


MEDICAL  AND  VETERINARY  ENTOMOLOGY 


Cotari^  rnouth  brushes 


head 


thora> 


abdomea' 


^abdominal 


anal  itpho.n 


Mdes  calopus  ]\Ieig.  {Stegomyia  fasciata  Fabr.),  with  which  we  are 
principally  concerned,  has  a  "lyre-like"  pattern  (Fig.  85d)  on  its  back 
(thorax),  i.e.  two  outer  curved  yellowish  white  lines  and  two  median 

parallel  lines.  The  legs  are  also 
conspicuously  banded,  the  distal 
portion  of  each  segment  being 
whitish  and  the  terminal  tarsal 
joint  entirely  white.  An  exami- 
nation of  the  head  in  this  genus 
shows  it  to  be  covered  with 
broad  flat  scales  (Fig.  79)  with 
only  a  single  row  of  upright 
forked  scales. 

The  yellow  fever  mosquito  is 
commonly  known  as  the  "  day- 
flying  mosquito."  This,  how- 
ever, only  applies  to  the  younger 
individuals  up  to  six  or  seven 
days,  after  which  they  become 
nocturnal  like  other  mosquitoes. 
The  distribution  of  the  yellow 
fever  mosquito  marks  it  as  a 
tropical  and  subtropical  species. 
Theobald  refers  it  to  38  degrees 
north  and  south  latitude.  How- 
ard ^  points  out  that  this  mos- 
quito "  does  not  thrive  below  a 
temperature  of  80°  F.,  so  that  in 
a  uniform  climate  with  a  tem- 
perature much  below  80°  the  species  will  not  continue  to  exist." 
The  same  author  also  states  that  it  is  probable  that  it  has  a  wide  range 
south  of  the  Mason  and  Dixon  line  in  the  United  States.  Yet  California, 
owing  probably  to  its  cold  nights,  is  free  from  this  species,  at  least 
north  of  San  Diego. 

The  yellow  fever  mosquito  is  typically  a  domestic  species,  found 
abundantly  in  towns.  Like  the  Anopheles  this  mosquito  is  silent  in  its 
flight.  It  is  said  to  be  extremely  wary.  Howard  observes  that  "  it 
prefers  the  blood  of  white  races  to  that  of  dark  races,  and  attacks 
young,  vigorous  persons  of  fine  skin  and  good  color  in  preference  to 
anaemic  or  aged  people." 

Eggs.  —  The  eggs  of  the  yellow  fever  mosquito  are  deposited  singly, 
are  dark  in  color  and  each  egg  is  surrounded  by  air  cells  (Fig.  82c). 
As  in  the  Anopheles  comparatively  few  eggs  are  deposited  at  one  laying, 
i.e.  from  perhaps  less  than  fifty  to  a  hundred,  and  there  may  be 
several  layings. 

1  Howard,  L.  O.,  1913.  The  Yellow  Fever  Mosquito,  U.  S.  Dept.  of  Agric, 
Farmers'  Bull.  547. 


combs  oT  pectens 
9'-*'  anal  seg 

tfacheal  «iUs 


Fig.  86.  —  A  mosquito  larva  with  parts  used 
in  classification  named.  (Adapted  after 
J.  B.  Smith.) 


MOSQUITOES 


95 


Unlike  the  eggs  of  most  species  these  can  withstand  desiccation  to  a 
very  marked  degree,  some  authors  declaring  that  this  is  possible  for 
several  months.     Ordinarily  the  eggs  hatch  in  about  forty-eight  hours. 

Larvae. —The  larvte  are  quite  stalky,  the  breathing  siphon  is 
comparati\'ely  short  and  heavy  (Fig.  856),  and  their  position  in  the  water 
is  almost  vertical,  considerably  more  so  than  other  Culicine  species. 
The  larval  stage  is  ordinarily  passed  in  about  nine  or  ten  days  under 
average  conditions. 

Pupae.  —  The  pupne  are  characteristically  Culicine;  the  breath- 
ing trumpets  are,  however,  broadly  triangular.  Only  about  thirty-six 
hours  is  spent  in  this  stage. 

Life  History.  —  The  yellow  fever  mosquito  breeds  by  preference 
in  artificial  pools  of  rain  water.  (They  are  known,  however,  at  times 
to  breed  naturally  in  brackish  water.)  Rain-water  barrels,  tanks, 
cisterns,  tin  cans,  urns,  etc.  provide  suitable  places,  also  water  collected 
between  the  leaves  of  certain  members  of  the  Agave  family ;  ornamental 
banana  palms  are  often  a  great 
menace  in  this  respect.  ^A- -.breathing  tTumpets 

According     to     Howard     the  )iJ~r>.^ thor^ii 

shortest    period    of    development  V'rfVo-v  W^-  - 

from  egg   to   imago   observed   by       c»se— -/ 

Reed   and   Carroll    in    Cuba   was     ^eai-— -vx  \n 

nine  and  a  half  days,  viz.:    egg         wm|^- 

stage,  two  days;  larval  stage,  six        ^     ^^^^^  ^.^>^??^^^^''7     \i 

days;     pupal     stage,     thirty-six 

hours.      From     this     very     short  ^^  -^;^ 

period  the  time  ranges  from  eleven 

to  eighteen  days  according  to  the      swvmmerets 

same  author. 

riflQcifirntinn      of     Mo<;nmtoeS       Fig.  87.  —  A  mosquito  pupa  with  parts  used 
UlaSSmcatlOn     OI     iVlOSqUlIOes.  .^  classification  named.     (Adapted   after 

—  The  principal  characteristics  on        j.  b.  Smith.) 
which    the   classification   of  mos- 
quitoes is  based  are  indicated  in  Figs.  86,  87  and  88,  together  with 
the  scale  characteristics  shown  in  Fig.  78  and  wing  venation  shown  in 
Fig.  71. 

The  following  key,  adapted  after  Stephens  and  Christophers  and 
Giles,  according  to  Theobald,  is  not  intended  to  be  comprehensive  and  is 
only  adapted  for  the  purpose  of  this  work.  For  a  complete  key  including 
all  known  mosquitoes,  the  reader  is  referred  to  Theobald's  Monograph 
of  the  CulicidcE  of  the  IFor/f/. 

Key  for  Classification  of  Mosquitoes 
A.   Scutellum  simple,  never  trilobed.     Proboscis  straight;  palpi  long  in  male 

and  female        Anophehna; 

AA.    Scutellum  trilobed  -in  n 

a    Proboscis   stronglv    recurved;     first   submarginal    cell    very   small 

Megarhininos 


96  MEDICAL  AND  VETERINARY  ENTOMOLOGY 


,'tArsus 


oasal  segment 

o^ab({omen 


";,>f''* tarsal  jo>t\\    \^/ 
.Ursa  I  daws- 

Fig.  88. — An  adult  mosquito  with  certain  parts  used  in  classification  named.      (Adapted 

after  J.  B.  Smith.) 


MOSQUITOES  97 

aa.   Proboscis  straight ;  metanotum  nude. 

1.  Wings  with  six  long  scaled  veins. 

2.  Antenna?  with  second  joint  normal  in  length. 

3.  First  submarginal  cell  as  long  or  longer  than  posterior  cell. 

4.  Palpi  of  female  shorter  than  proboscis,  of  the  male  long   Culicince 
4'.  Palpi  short  in  male  and  female J^dincB 

Subfamily  Anophelin^b 

Table  of  Genera 

First  submarginal  cell  large 
I.   Antennal  segments  without  dense  lateral  scale  tufts 

a.  Thorax  and  abdomen  with  hair-like  curved  scales.     No  flat  scales 

on  head,  but  upright  forked  ones. 
Basal  lobe  of  male  genitalia  of  one  segment 

1.  Wing  scales  large,  lanceolate      .     .     Genus  Anopheles  Meigen 

2.  Wing  scales  mostly  small,  long  and  narrow  or  slightly  lanceolate 

Genus  Myzomyia  Blanchard 

3.  Wings  with  patches  of  large  inflated  scales 

Genus  Cycloleppteron  Theobald 
Basal  lobe  of  two  segments 

4.  Prothoracic  lobes  with  dense  outstanding  scales 

.  Genus  Feltinella  n.  g. 
Median  area  of  head  with  some  flat  scales ;   prothoracic  lobes  mam- 
millated 

5.  Wing  scales  lanceolate      .     .     .    Genus  Stethomyia  Theobald 

b.  Thorax  with  narrow  curved  scales ;  abdomen  hairy 

6.  Wing  scales  small  and  lanceolate;    head  with  normal  forked 

scales        Genus  Ptjretophorus  Blanchard 

7.  Wing  scales  broad  and  lanceolate ;  head  with  broad  scales,  not 

closely  appressed  but  not  forked  or  fimbriated 

Genus  Myzorhynchella  n.  g. 

c.  Thorax  with  hair-like  curved  scales  and  some  narrow-curved  ones 

in  front ;   abdomen  with  apical  lateral  scale  tufts  and  scaly 
venter ;  no  ventral  tuft. 

8.  Wing  scales  lanceolate     .     .     .     Genus  Am6afea^i'a  Theobald 

d.  Thorax  with  hair-like  curved  scales ;   no  lateral  abdominal  tufts ; 

distinct  apical  ventral  tuft.     Palpi  densely  scaly. 

9.  Wing  with  dense  large  lanceolate  scales 

Genus  Myzorhynchus  Blanchard 

e.  Thorax  with  hair-like  curved  scales  and  some  narrow  curved  lateral 

ones ;  abdomen  hairy  with  dense  long  hair-like  lateral  apical 
scaly  tufts.  . 

10.  Wing  scales  short,  dense,  lanceolate ;   fork  cells  short. 

Genus  Christija  Theobald 
/.   Thorax  with  very  long  hair-like  curved  scales ;  abdomen  with  hairs 
except  last  two  segments  which  are  scaly.     Dense  scale  tufts 
>  to  hind  femora. 

11.  Wings  with  broadish,  blunt  lanceolate  scales 

Genus  Lophoscelornyia  Theobald 
g.  Thorax  and  abdomen  with  scales 

12.  Thoracic  scales,  narrow-curved  or  spindle-shaped ;   abdominal 

scales  as  lateral  tufts  and  small  dorsal  patches  of  flat  scales 

Genus  Nyssorhynchus  Blanchard 

13.  Abdomen  nearly  completely  scaled  with  long  irregular  scales 

and  with  lateral  tufts       ....     Genus  Cellia  Theobald 


98         MEDICAL  AND   VETERINARY  ENTOMOLOGY 

14.  Similar  to  above,  but  no  lateral  scale  tufts     Genus  Neocellia,  n.  g. 

15.  Abdomen  completely  scaled  with  large  flat  scales  as  in  Culex 

Genus  Aldrichia  Theobald 

16.  Thoracic  scales  hair-like,  except  a  few  narrow-curved  ones  in 

front ;  abdominal  scales  long,  broad  and  irregular 

Genus  Kerteszia  Theobald 
II.         17.  Antennal  segments  with  many  dense  scale  tufts 

Genus  Chagasia  Cruz 
A  A.  18.  First  submarginal  cell,  verj^  small     Genus  Biro7iellaTheoha\d 

Genus  Anopheles 
Table  of  Species 

a.  Wi7igs  spotted,  legs  unhanded,  casta  unspotted. 

1.  A.  maculipennis  —  Wing  field  four  spots.  Palpi  unhanded.  Europe, 
giving  way  to  A.  quadrimaculatus  in  North  America. 

2.  A.  crucians  —  White  spots  on  dark  veins.  Three  dark  spots  on  sixth 
vein.     Tarsi  unhanded ;   palpi  three  white  bands.     North  America. 

3.  A.  eiseni — -Apical  fourth  of  hind  tibia?  yellowish.  Sixth  vein  wholly 
black.     Guatemala. 

aa.  Wings  spotted,  legs  unhanded,  casta  spotted. 

4.  A.  punctipennis  —  Costa,  characteristic  yellow  spot  near  apical  fourth  of 
wing  fringe ;  no  spots.     North  America. 

5.  A.  pseudopunctipen7iis  —  Wings  as  in  previous  species  but  wing  fringe 
with  several  yellow  spots ;   (?)  a  distinct  species.     North  America. 

6.  A.  franciscanus  —  Small  species ;  costa,  a  spot  about  middle,  and  a  pure 
yellow  apical  spot;  third  vein  white  with  two  black  spots.  Fringe  spotted. 
North  America. 

aaa.  Wings  spotted,  legs  banded. 

7.  A.  gigas  —  Costa,  two  large  costal  spots.  Legs  with  pale  basal  bands. 
A  hill  species.     India. 

8.  A.  wellcomei  —  Costa,  two  small  yellowish  spots.  Legs  with  narrow 
apical  bands.     Sudan. 

9.  xi.  arabiensis  —  Costa,  seven  dark  spots,  four  long  and  three  short. 
Other  veins  much  spotted.  Fringe  spots  at  all  the  vein  junctions.  Hind  femur 
and  tibia  speckled  —  latter  often  has  apical  band.  Palpi  three  white  bands. 
Markings  vary  according  to  season.     Arabia. 

10.  A.  dthali — ^  Costa,  four  black  spots,  the  basal  the  longest.  First  long 
vein  four  black  spots,  other  veins  pale.  Wing  fringe,  no  spots.  Palpi,  pale 
with  two  white  bands.     Arabia. 

aaaa.  Wings  unspotted,  legs  unhanded,  thorax  with  abnormal  pattern. 

11.  A.  corethroides  —  resembles  A.  bif meatus,  but  differs  in  (a)  thorax  being 
pale  brown  with  a  large  median  anterior  dark  area,  and  a  long  lateral  dark  area 
behind  this  as  in  Corethra.     S.  Queensland. 

12.  A.  bifurcatus  —  abdomen  with  golden  hairs,  thorax  with  two  broad  bare 
lines  in  front.     Europe. 

13.  A.  algeriensis  —  abdomen  with  brown  hairs,  lateral  scales  of  veins  longer 
and  finer  than  in  .4.  bifurcatus.  Anterior  and  posterior  cross  veins  in  same 
line  in  both  sexes.  In  A.  bifurcatus  the  posterior  is  internal  in  female,  the 
anterior  in  male.     Africa. 

14.  .4.  barberi  —  differs  from  previous  two  in  having  stalk  of  first  fork  cell 
equal  to  instead  of  greater  than  one  third  length  of  cell.  The  larva  lives  in 
holes  in  trees.     Maryland,  U.  S.  A. 

aaaaa.  Wings  unspotted,  legs  unhanded,  thorax  with  normal  pattern,  second 
fork  cell  exceeds  half  length  of  first,  palpi  banded. 


MOSQUITOES  99 

15.  A.  smithi  —  Wing  scales  very  dense.     Sierra  Leone. 

16.  A.  nigripes  —  Not  so  dense  as  in  previous  species.    Thorax,  gray  mark- 
ings.    Europe,  America. 

aaaaaa.  Wings  unspotted,  legs  unhanded,  thorax  with  normal  pattern,  second 
fork  cell  does  not  exceed  half  the  length  of  the  first. 

17.  A.  aitkeni.     Bombay  presidency. 
aaaaaaa.  Wings  unspotted,  legs  banded. 

18.  A.  lindesayi  —  A  dark  species.     Costa,   black,  apical  white  spot ;   hind 
femora  with  characteristic  broad  white  band.     Hill  species  chiefly.     India. 

19.  A.  immacidatus  —  An  ash-gray  species.     Slight  apical  bandings  to  tarsi. 
Palpi  and  proboscis  lighter  at  apex.     A  very  rare  species.     Ennur,  Madras. 

•  Subfamily  Megarhinin^ 

Table  of  Genera 

a.  Palpi  5-jointed  in  female  (long)  Genus  Megarhince 

b.  Palpi  3-jointed  in  female  (comparatively  short)  Genus  Toxorhynchites 

Subfamily  CuLiciNiB 
Table  of  Genera 

a.   Legs  more  or  less  densely  scaled. 

Posterior  cross  vein  nearer  the  base  than  the  mid  cross  vein ;  hind  legs  with 
tarsi  in  male  densely  long  scaled ;  wing  scales  long  and  rather  thick 

Genus  Eretmapodites 

Cross  vein  as  in  Culex ;  scales  of  crown  and  occiput  broadly  spindle-shaped  ; 

3d  long  vein  continued  as  distinct  pseudovein  into  the  basal  cell 

Genus  Janthinosonia 
Posterior  cross  vein  nearer  base  of  wing  than  mid  cross  vein ;   wings  with 

thin  scales Genus  Psorophora 

Posterior  cross  vein  nearer  apex  of  wing  than  mid  cross  vein ;   wings  with 

large  pyriform  parti-colored  scales Genus  Muscidus 

aa.   Legs  uniformly  clothed  with  flat  scales. 

Scales  of  the  wings  very  large,  flat,  broad,  asymmetrical    Genus  Panoplites 
Scales  of  wings  dense,  lateral  ones  large,  elongated  oval  or  lanceolate 

Genus  Tceniorhynchus 
Metanotum  nude,  scales  of  wings  much  as  in  Tceniorhynchus,  metanotum 
with  a  tuft  of  chetse  and  with  patches  of  flat  scales 

Genus  Trichoprosopon 
b.   Head  and  scutellar  scales  all  flat  and  broad. 

Third  long  vein  as  an  incrassation  into  the  basal  cell   Genus  Armigeres 
bb.   Nape  clothed  with  mixed  narrow,  curved,  and  upright  forked  scales, 
with  small  lateral  patches  of  flat  scales. 
Second  antennal  joint  small  or  moderate-sized 

Scales  of  the  wings  small,  lateral  ones  linear   ....     Genus  Culex 
Second  antennal  joint  very  long,  distal  joints  without  scales 

Genus  Deinokerides 
Second  antennal  joint  very  long,  2d  to  5th  joints  clothed  with  scales 

Genus  Brachiomyia 
Subfamily  ^din^ 

Table  of  Genera 

A.  Proboscis  formed  for  piercing ;  metanotum  nude. 

a.   Palpi  three  to  five  jointed.     Body  showing  generally  a  distinct  metallic 
luster.     One  or  more  of  the  legs  provided  with  a  paddle-shaped  expan- 


100        MEDICAL  AND   VETERINARY   ENTOMOLOGY 

sion,  formed  of  elongated  scales,    "3"  nearer  apex  of  wing  than 
"4c";    "2"   nearer  apex  than  "3";   III  extended  into  basal  cell 

Genus  Sabethes 

b.  Palpi  two  or  three  jointed ;  non-metallic. 

Wing  scales  large  and  flat,  and  bracket-shaped;    fork  cells  normal 

Genus  Mdomyia 
Wing  scales  small,  linear  like  Culex ;    fork  cells  normal      Genus  /Edes 

c.  Palpi  five-jointed ;    fork  cells  normal ;    metallic     Genus  Hceynagogus 

d.  Palpi  two-jointed ;   fork  cells  very  small ;   with  metallic  spots  of  flat 

scales  on  the  thorax  and  elsewhere      ....     Genus  Urajiotcenia 

B.  Proboscis  formed  for  piercing ;  metanotmn  armed  with  cheta; :  palpi  small. 

Proboscis  rather  or  very  long Genus  Wyeomyia 

A  convenient  key  for  the  identification  of  eggs,  larva?  and  pupa?  may  be  found 
in  Mosquito  Life  by  Mitchell,^  pp.  216-258. 

1  Mitchell,  Evelyn  G.,  1907.     Mosquito  Life.     G.  P.  Putnam's  Sons,  N.  Y., 
pp.  xxii  -1-  281. 


CHAPTER   X 
MOSQUITOES  AS  DISEASE  BEARERS 
•  A.    Malaria 

Malaria.  —  Malaria  is  a  widely  distributed  disease,  prevalent  to  a 
greater  or  less  degree  on  every  continent.  While  not  restricted  to  the 
lowlands,  it  does  not  occur  extensively  at  high  altitudes,  primarily 
because  of  the  lower  temperature,  i.e.  the  disease  requires  an  average 
summer  temperature  of  not  less  than  60°  F.  There  are,  however, 
situations  in  which  it  is  known  to  occur  at  an  elevation  of  3000  feet, 
notably  in  Java  and  Madagascar. 

Malaria  is  also  commonly  known  as  ague,  chills  and  fever,  inter- 
mittent fever,  remittent  fever,  jungle  fever,  paludism,  etc.  The 
symptoms,  even  though  slight,  are  usually  manifested  in  the  form  of  a 
regularly  appearing  paroxysm  consisting  of  three  fairly  well-defined 
stages,  viz. :  the  cold  stage  (the  chill)  in  which  the  skin  becomes  pale 
and  has  the  appearance  of  "  gooseflesh,"  the  patient's  teeth  may  chatter, 
and  he  may  shiver  more  or  less  violently ;  the  next  stage  is  the  hot 
stage  or  fever,  the  temperature  rising  during  the  chill,  the  skin  is  hot  and 
flushed ;  the  third  stage  is  marked  by  the  appearance  of  a  general 
perspiration,  the  fever  falls,  and  the  patient  becomes  normal.  The 
entire  paroxysm  may  last  but  a  few  hours.  In  many  cases  the  stages 
are  not  so  well  marked,  neither  do  the  paroxysms  recur  at  exactly  the 
same  interval,  • —  the  latter  depends  largely  on  the  type  of  infection. 

The  disease  is  caused  by  blood-inhabiting  Protozoa  belonging 
to  the  genus  Plasmodium.  These  parasites  attack  the  red  corpuscles, 
destroying  the  same  while  reproducing  asexually;  this  asexual  repro- 
duction or  sporulation  occurs  at  fairly  regular  intervals,  i.e.  twenty- 
four,  forty-eight,  or  seventy-two  hours,  depending  upon  the  species  of 
Plasmodium  involved,  the  paroxysm  resulting  at  corresponding  times. 
That  the  paroxysm  is  due  not  to  the  destruction  of  the  myriads  of  cor- 
puscles at  a  given  time,  but  to  the  liberation  of  a  toxin  produced  by  the 
intracorpuscular  parasites,  is  now  generally  believed. 

Historical.  —  Malaria,  though  not  receiving  its  name  until  the 
middle  of  the  eighteenth  century,  has  been  known  for  many  centuries, 
Hippocrates  having  divided  periodic  fevers  into  the  quotidian  (daily), 
tertian  (every  third  day)  and  quartan  (every  fourth  day).  The  fable 
of  Hercules  and  the  Hydra  is  believed  to  refer  to  malaria,  and  the 

101 


102        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

disease  is  mentioned  in  the  Orphic  poems.  The  successful  treatment  of 
malaria  dates  back  previous  to  the  seventeenth  century.  The  Countess 
del  Cinchon,  the  wife  of  the  Viceroy  of  Peru,  was  cured  of  fever  in  1638 
by  the  use  of  the  bark  from  a  certain  tree.  This  bark  was  introduced 
into  Europe  in  1640,  and  in  1741  Linne  named  it  "cinchona"  in  honor 
of  the  Countess  del  Cinchon.  In  1753  Torti  named  the  disease 
"malaria,"  believing  it  to  be  air  borne  and  emanating  from  the  bad  air 
(vial  aria)  rising  from  swamps  and  marshes. 

The  credit  for  the  discovery  of  the  causative  organism  belongs  to 
Laveran,  a  French  army  surgeon  who  was  stationed  in  Algeria.  This 
discovery  was  made  in  1880.  Although  the  mosquito  transmission 
theory  is  said  to  have  been  held  for  many  years  among  the  Italian  and 
Tyrolese  peasants  and  the  natives  of  German  East  Africa,  the  first  well 
formulated  mosquito-malaria  theory  was  advanced  by  King  in  1883. 
In  1885  Golgi  discovered  that  the  periodicity  of  the  fevers  corresponded 
to  the  periodic  sporulation  of  the  Plasmodium. 

Nuttall  (1899)  refers  to  the  interesting  fact  that  the  malaria-mos- 
quito theory  has  been  repeatedly  rediscovered  by  writers  in  various 
countries,  e.g.  Laveran  first  mentioned  the  theory  in  1891,  Koch  (ac- 
cording to  Pfeiffer)  in  1892,  Manson  in  1894,  Bignami  and  Mendini  in 
1896  and  Grassi  in  1898. 

The  greatest  discovery  in  the  history  of  malaria  (as  evidenced  by  the 
fact  that  two  Nobel  prizes  have  been  awarded  the  discoverer)  was  made 
by  the  Englishman,  Major  Ronald  Ross,  in  1898,  then  stationed  in  India. 
Ross  demonstrated  beyond  doubt  the  important  role  played  by  mos- 
quitoes in  the  transmission  of  malaria,  and  mankind  owes  no  greater 
debt  to  a  fellow  man  than  this.  Late  in  the  same  year  Grassi  proved 
that  malaria  can  only  be  transmitted  by  a  particular  kind  of  mosquito, 
namely.  Anopheles. 

In  1900,  at  the  suggestion  of  Sir  Patrick  Manson,  Doctors 
Sambon  and  Low  built  a  mosquito-proof  hut  in  the  Roman 
Campagna,  in  which  they  lived  during  the  most  malarial  months  of 
that  year  without  contracting  malaria.  At  this  time  these  investi- 
gators sent  infected  Anopheles  mosquitoes  from  the  Campagna  to 
London,  where  Doctor  Manson's  son.  Dr.  P.  Thurburn  Manson,  and  Mr. 
George  Warren  permitted  themselves  to  be  bitten  by  these  mosquitoes 
and  in  due  time  became  ill  with  the  disease. 

The  use  of  oil  as  a  factor  in  mosquito  control  dates  back  to  the 
beginning  of  the  nineteenth  century;  however,  the  present  extensive 
use  of  kerosene  for  this  purpose  is  due  largely  to  the  efforts  of  Howard, 
beginning  in  1892. 

While  certain  German  investigators  claimed  to  have  reared  the 
malaria  parasite  in  vitro  previously,  it  appears  that  the  first  recorded 
successful  attempts  to  accomplish  this  were  made  by  Bass  in  1911. 

Circumstantial  Evidence.  —  Immediately  following  great  spring 
floods  when  the  valleys  become  inundated  and  the  receding  water 


.  MOSQUITOES  AS   DISEASE   BEARERS  103 

leaves  behind  it  innumerable  pools  and  overflowed  cellars  and  cess- 
pools, there  is  always  much  more  malaria  than  usual,  a  fact  always 
predicted.  Coincidentally  mosquitoes  are  unusually  abundant,  and 
especially  the  noiseless  kind.  Exceedingly  warm  moist  seasons  always 
bring  more  malaria,  while  a  prolonged  drought  is  commonly  said  to 
kill  the  disease,  as  does  the  approach  of  cold  weather. 

A  very  common  suggestion  made  to  escape  malaria  is  to  keep  out 
of  the  "  night  air  "  and  close  windows  and  all  openings  which  might  per- 
mit the  "  night  air  "  to  enter. 

In  localities  where  anti-mosquito  campaigns  have  been  waged  with 
vigor  there  has  quickly  followed  a  decrease  in  malaria,  no  other  pre- 
cautions having  been  taken. 

The  circumstantial  evidence  against  the  mosquito  (in  a  broad  sense) 
may  be  summed  up  as  follows : 

(1)  Malaria  exists  endemically  in  districts  where  mosquitoes  are 
present  (all  species  except  the  Anophelines  are  eliminated  experimen- 
tally) ;  (2)  malaria  does  not  exist  endemically  where  there  are  no 
mosquitoes  (existing  cases  are  without  exception  traced  to  an  earlier 
visit  on  the  part  of  the  patient  to  some  locality  in  which  mosquitoes  of 
the  Anopheline  type  occur) ;  (3)  persons  protecting  themselves  against 
mosquito  bites  while  dwelling  in  malarial  districts  (otherwise  living  as 
do  the  natives)  do  not  contract  malaria ;  (4)  communities  previously 
noted  for  malaria  have  been  practically  freed  from  this  disease  when 
efficient  drainage  (sewer)  systems  have  been  installed ;  (5)  properly 
conducted  mosquito  crusades  result  in  the  elimination  of  about  50  per 
cent  of  the  cases  of  malaria  within  that  district  in  the  same  season.  (The 
existing  cases  can  be  accounted  for  through  relapses  and  exposure  to 
mosquito  bites  outside  the  protected  district.) 

It  may  be  said  that  malaria  may  be  wholly  absent  in  the  presence 
of  an  abundance  of  mosquitoes.  In  answer  to  this  it  may  be  replied 
that  there  are  several  hundred  species  of  mosquitoes,  of  which  number 
only  one  or  two  species  for  any  one  locality  are  capable  of  transmitting 
malaria.  Hence,  first,  the  mosquitoes  in  such  localities  are  probably 
all  non-malaria-bearing,  with  the  entire  absence  of  the  malaria-bear- 
ing species  (Anopheline),  or,  secondly,  if  Anopheline  mosquitoes  are 
present,  they  have  not  become  infected  by  the  importation  of  persons 
affected  with  malaria,  i.e.  malaria  must  first  be  introduced  before  the 
Anopheline  mosquitoes  can  carry  it  from  person  to  person. 

Experimental  Evidence.  —  The  parasite  of  malaria  can  easily  be 
^een  by  examining  microscopically  properly  stained  blood  from  infected 
persons.  The  disease  can  be  produced  experimentally  in  healthy 
persons  by  inoculation  with  parasitized  blood  taken  from  a  malarial 
patient. 

Malaria  is  popularly  believed  to  be  present  in  certain  sources  of 
drinking  water,  also  in  overripe  fruit.  This  was  the  case  in  two  com- 
munities in  California  in  which  it  was  proposed  to  control  the  disease 


104        MEDICAL  AND  VETERINARY  ENTOMOLOGY 

by  combating  mosquitoes.  The  sanitary  inspectors  drank  this  water, 
ate  freely  of  the  ripest  fruit  and  were  exposed  to  the  severest  heat  of 
the  day  and  remained  free  from  malaria,  having  exercised  the  proper 
night  precautions.  That  miasma  from  swamps  has  no  direct  relation 
to  malaria  was  proved  by  Sambon  and  Low,  as  already  noted. 

It  is  well  known  that  blood  taken  directly  from  a  patient  suffering 
from  malaria  may  show  flagellated  parasites.  Ross,  in  1895,  in  his 
Indian  observations  found  these  flagellated  bodies  in  the  intestines  of 
mosquitoes  which  had  fed  on  the  blood  of  malarial  patients.  Many 
experiments  were  made  and  hundreds  of  mosquitoes  examined  during 
the  next  few  years  by  Ross.  The  most  striking  condition  found  in  some 
of  these  mosquitoes  was  the  development  of  pigmented  cells  in  the 
stomach  wall,  the  pigment  corresponding  to  malaria  pigment  Some  of 
these  mosquitoes  gave  positive  results,  while  the  majority  gave  nega- 
tive results.  Those  which  furnished  positive  results  were  of  a  particu- 
lar species,  and  this  gave  the  clew  that  the  malaria  parasite  required  a 
particular  species  of  mosquito  to  serve  as  intermediary  host.  The  con- 
nection between  the  flagellated  bodies  and  the  pigmented  cells  was  fur- 
nished by  MacCallum  in  1898.  He  found  that  the  function  of  the 
flagellated  cells  was  that  of  an  impregnating  body ;  that  each  flagellum, 
of  which  there  were  several  to  each  cell,  impregnated  a  spherical  para- 
site. MacCallum's  observations  were  made  on  the  Proteosoma  of  birds, 
also  known  as  "bird  malaria."  Using  the  Proteosoma  as  a  basis  for 
his  further  observations,  Ross  found  that  the  pigmented  cells,  migrating 
through  the  stomach  wall  of  the  mosquito  ^  and  encysting  just  beneath 
the  peritoneal  lining,  grew  steadily  for  three  or  four  days,  forming  spindle- 
shaped  bodies,  which  were  shed  into  the  body  cavity  and  in  six  or  seven 
days  after  feeding  were  found  in  vast  numbers  in  the  salivary  glands. 

Grassi's  experiments  in  the  Roman  Campagna  and  Sicily  proved  that 
human  malaria  was  carried  solely  by  Anopheline  mosquitoes.  Accord- 
ing to  Nuttall  one  of  the  early  experiments  of  Grassi  and  Bignami  was 
conducted  somewhat  as  follows :  Three  species  of  mosquitoes,  Ciilex 
penicillaris,  Culex  malarioB  and  Anopheles  claviger  were  collected  in  a 
malarial  district,  Maccarese,  22  miles  from  Rome.  The  insects  were 
then  allowed  to  bite  a  patient  (who  consented  to  the  experiment)  in  the 
Santo  Spirito  Hospital  (Rome).  The  patient  had  never  had  malaria. 
In  addition  to  the  bites  from  the  imported  insects  the  man  was  also 
subjected  to  the  bites  of  mosquitoes  emerging  from  larvae  placed  in  the 
room  occupied  by  him  at  night.  A  new  supply  of  larvae  was  placed  in 
the  room  every  four  to  six  days.  In  due  time  the  man  acquired  jestivo- 
autumnal  malaria  as  evidenced  by  the  appearance  of  parasites  in  his 
blood.  Grassi  believed  that  the  disease  was  due  to  the  bites  of  Culex 
penicellaris  because  it  was  the  most  numerous,  while  Anopheles  claviger 

1  It  should  be  noted  here  that  certain  Culicine  mosquitoes  (Culex  pipiens) 
are  the  transmitters  of  Proteosoma  though  inefficient  as  transmitters  of  Plas- 
modium or  human  malaria. 


MOSQUITOES  AS  DISEASE   BEARERS  105 

was  present  in  very  small  numbers.  Nuttall  remarks  that  the  infection 
could  only  have  been  produced  by  the  latter,  as  has  been  determined 
since. 

After  describing  the  conditions  under  which  Sambon  and  Low  lived 
in  the  Roman  Campagna  while  experimenting  with  malaria,  Manson  ^ 
writes  as  follows :  "  Whilst  this  experiment  was  in  progress  mosquitoes 
fed  in  Rome  on  patients  suffering  from  tertian  malaria  were  forwarded 
in  suitable  cages  to  the  London  School  of  Tropical  Medicine,  and  on 
their  arrival  were  set  to  bite  my  son,  the  late  Dr.  P.  Thurburn  Manson, 
and  Mr.  George  Warren.  Shortly  afterwards  both  of  these  gentlemen, 
neither  of  whom  had  been  abroad  or  otherwise  exposed  to  malarial 
influences,  developed  characteristic  malarial  fever,>  and  malarial  para- 
sites were  found  in  abundance  in  their  blood,  both  at  that  time  and  on 
the  occurrence  of  the  several  relapses  of  malarial  fever  from  which  they 
subsequently  suffered.  The  mosquito-malaria  theory  has  now,  there- 
fore, passed  from  the  region  of  conjecture  to  that  of  fact." 

The  Parasite.  —  The  malarial  parasites  (Plasmodia)  belong  to  the 
lowest  forms  of  animal  life,  the  Protozoa  (Subphylum  Sporozoa,  Class 
Telosporida,  Subclass  Hsemosporida).  The  pigment  of  these  red-blood- 
corpuscle-inhabiting  parasites  is  dark  and  characteristic  and  properly 
termed  melanin.  The  presence  of  the  parasites  usually  gives  rise  to  a 
periodic  chill  and  fever,  due  to  their  periodic  asexual  reproduction 
(sporulation)  and  the  liberation  of  a  toxin  in  the  human  blood. 

To  detect  the  presence  of  the  parasite  a  drop  of  blood  is  drawn  from 
the  lobe  of  the  patient's  ear  or  finger  tip,  after  proper  cleansing  with 
alcohol ;  the  droplet  of  blood  is  lightly  touched  with  a  glass  microscopi- 
cal slide,  upon  which  a  film  (smear)  is  made  by  gently  and  evenly  spread- 
ing the  droplet  by  means  of  a  needle  or  edge  of  another  slide.  The  film 
is  then  fixed  and  stained,  using  Romanowsky  modifications,  such  as 
Wright  and  Leishman,  also  Giemsa  and  Jenner.  If  parasites  are  pres- 
ent in  the  blood,  they  should  be  visible  after  careful  microscopical  exam- 
ination as  pigmented  intracorpuscular  bodies  in  the  form  of  signet 
rings,  amoeboid  forms  or  as  crescents  in  sestivo-autumnal  fever  of  ten 
or  more  days'  duration.  Microscopic  examination  under  an  oil  im- 
mersion lens  is  desirable,  though  crescents  can  easily  be  seen  with  lower 
powers. 

The  ease  with  which  parasites  can  be  discovered  in  a  blood  smear 
depends  on  several  important  factors,  —  first,  on  the  length  of  time  that 
the  patient  has  had  malaria,  and  secondly  on  the  condition  that  he  has 
lately  taken  quinine  when  the  chances  for  the.  discovery  of  parasites  is 
reduced  practically  to  nil.  Ross  ^  states  that  the  parasites  "  will  not 
generally  be  numerous  enough  to  cause  illness  unless  there  is  at  least 

1  Manson,  Sir  Patrick,  1909.  Tropical  Diseases.  Cassell  and  Company 
(London),     pp.  xx  +  876. 

2  Ross,  Ronald,  1910.  The  Prevention  of  Malaria.  E.  P.  Button  &  Com- 
pany, New  York.     pp.  xx  +  668. 


106        MEDICAL  AND   VETERINARY  ENTOMOLOGY 


one  parasite  to  100,000  hsematids ;  that  is,  50  parasites  in  1  cmm.  of 
blood;  or  150,000,000  in  a  man  64  kilograms  in  weight.  .  .  .  Such 
calculations  demonstrate  the  absurdity  of  supposing  that  there  are  no 
Plasmodia  present  in  a  person  because  we  fail  in  finding  one  after  a  few 
minutes'  search.  As  a  matter  of  fact,  even  if  as  many  as  150,000,000 
Plasmodia  are  present  in  an  average  man,  the  chances  are  that  ten  to  fif- 
teen minutes'  search  will  be  required  for  each  plasmodium  found ;  while 
if  we  are  careless  or  unfortunate,  we  may  have  to  look  much  longer." 
The  various  types  of  malaria  are  due  to  the  fact  that  there  are 
several  species  of  parasitic  plasmodia,  each  of  which  produces  specific 


Fig.  89.  —  To  illustrate  detection  of  malaria  parasite,  a.  normal  unparasitized  red  blood 
corpuscle  ;  b.  young  intracorpuscular  parasite  ;  c.  signet  ring  ;  d.  intracorpuscular  cres- 
cent;   e.  free  female  crescent ;  /.  free  male  or  hyaline  crescent ;   g.  female  oval. 

symptoms.  Three  or  possibly  four  distinct  types  are  usually  recog- 
nized :  (1)  /Estwo-autumnal  or  Malignant  Tertian;  (2)  Tertian  or 
Benign  Tertian;    (3)  Quartan,  and  (4)  Quotidian. 

a.  Plasmodium  yrcecox  Dofl.  {Hwmamoeba  prcecox  Grassi  et  Fe- 
letti,  Plasmodium  falciparum  Welch)  is  the  cause  of  aestivo-autumnal 
fever  (malignant  tertian  fever)  of  the  tropics  and  subtropics  with  the 
paroxysm  recurring  every  forty-eight  hours.  The  pigment  granules 
in  this  species  are  relatively  few  and  very  coarse.  The  infected  red  cor- 
puscle is  usually  normal  in  size,  but  may  be  slightly  shrunken  and 
crenated.  The  segmenting  stage,  which  is  rarely  seen  in  the  peripheral 
blood,  is  said  to  produce  only  from  eight  to  ten  merozoites,  according  to 
Stephens  and  Christophers,  or  from  five  to  twenty-five  and  over  accord- 


MOSQUITOES  AS  DISEASE   BEARERS 


107 


ing  to  Deaderick.  Characteristic  crescents  (Fig.  89)  or  gametocytes 
(immature  sexual  forms)  are  commonly  observed  in  cases  of  ten  or  more 
days'  duration.  Crescents  occur  in  this  species  only.  The  female  cres- 
cents show  the  chromatin  granules  well  concentrated  in  the  mid-region, 
with  slight  stippling  at  both  ends,  while  the  male  crescents  have  the 
chromatin  thinly  scattered  with  both  ends  hyaline  (they  are  also  called 
hyaline  bodies  or  hyaline  crescents).  Certain  relapses  after  months  of 
latency  are  said  to  be  traceable  to  a  parthenogenetic  cycle,  in  which  the 
female  crescents  produce  merozoites  asexually,  which  now  attack  the  red 
blood  corpuscles,  as  do  the  ordinary  sporulated  forms.  Sporulation 
occurs  about  every  forty-eight  hours. 

b.  Plasmodium  vivax  Grassi  et  Feletti  (Hooviamoeba  vivax  Grassi  et 
Feletti)  is  the  cause  of  tertian  fever  or  benign  tertian  malaria  of  temper- 


FiG.   90.  —  Signet  ring  stage  of  malaria  parasite. 


ate  climates,  occurs  also  abundantly  in  the  tropics  and  subtropics, 
with  recurrent  paroxysms  regularly  every  forty-eight  hours.  In  these 
parasites  the  pigment  granules  are  very  fine  and  are  distributed  through- 
out the  red  corpuscles  as  Schiiffner's  dots.  The  parasitized  corpuscles 
are  distinctly  enlarged  and  are  quite  pale.  The  parasites  are  bizarre  in 
form.  There  are  no  crescents  in  this  species,  and  the  gametocytes  are 
not  easily  distinguishable  from  the  asexual  parasites,  except  for  their 
more  regular  form  and  denser  pigmentation.  The  number  of  elements 
in  the  sporulating  or  segmented  stage  commonly  seen  in  the  peripheral 
blood  is  larger  than  in  the  former,  and  their  arrangement  is  irregular 
(fifteen  or  more,  according  to  Stephens  and  Christophers) .  Sporulation 
occurs  regularly  every  forty-eight  hours. 


108        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

c.  Plasmodium  malaria;  Laveran  {Laverania  malariae  Grassi  et 
Feletti,  Hamamosba  malarioe  Grassi  et  Feletti)  is  the  cause  of  quartan 
fever,  with  recurrent  paroxysms  every  seventy-two  hours.  This  form 
of  malaria  is  comparatively  rare,  and  coincides  in  distribution  with 
gestivo-autumnal  fever.  The  pigment  is  coarse  and  generally  occurs  in 
marginal  streaks  or  in  bands.  The  parasitized  corpuscles  are  usually 
normal  in  size,  and  the  parasite  is  more  or  less  oval  in  shape.  The 
gametocytes  are  rarely  seen.  The  segmenting  stage  gives  rise  to  the 
typical  "  daisy  "  form,  each  sporulated  body  radiating  from  the  center. 
The  number  of  bodies  varies  from  six  to  twelve,  oftenest  eight  (Dea- 
derick).     Sporulation  occurs  every  seventy-two  hours. 

d.  Plasmodium  falciparum  quotidianum  Craig  is  believed  to  be  the 
causative  organism  of  quotidian  malaria,  with  paroxysms  recurring  every 
twenty-four  hours.  This  must  not  be  confused  with  multiple  infec- 
tion on  the  part  of  other  species  of  Plasmodia  which  might  also  result 
in  daily  paroxysms.  This  type  of  malaria  occurs  in  practically  all 
parts  in  which  testivo-autumnal  fever  occurs.  The  parasite  resembles 
Plasmodium  prwcox  ( =  P.  fahiiMrum)  very  closely,  but  the  infected  cor- 
puscles are  said  to  be  considerably  smaller  than  normal,  and  are  usually 
brassy  in  appearance. 

The  signet  ring  (Fig.  90)  is  the  earliest  stage  in  the  development  of 
the  intracorpuscular  parasite  of  all  species,  and  is  characterized  by  a 
blue  staining  ring  with  a  heavy  chromatin  dot  (the  nucleus)  at  or  near 
the  thinner  segment.  The  thickness  of  the  wider  segment  varies  with 
the  species,  e.g.  in  the  large  conspicuous  rings  of  both  P.  vivax  and 
P.  malaria;,  the  rings  are  quite  thick  and  the  dot  is  usually  situated  in 
a  line  with  the  thinner  segment ;  in  P.  prcecox  the  rings  are  smaller  and 
thinner  and  the  chromatin  dot  (commonly  double)  is  frequently  out  of 
line  with  the  ring.  There  may  be  two  and  even  three  rings  inside  of  one 
corpuscle. 

Life  History  of  the  Plasmodium.  —  The  life  history  of  malaria  Plas- 
modia involves  two  distinct  cycles ;  namely,  first,  the  asexual,  also  known 
as  the  human  cycle,  cycle  of  Golgi  or  schizogonic  cycle ;  and  secondly, 
the  sexual,  also  known  as  the  mosquito  cycle,  cycle  of  Ross  or  sporogonic 
cycle.  A  third  cycle  which  explains  the  recurrence  of  malaria  after 
longer  periods  of  latency  is  known  as  the  parthenogenetic  or  virgin  cycle, 
passed  within  the  human  body. 

The  asexual  cycle  (Fig.  91,  1-6),  passed  within  the  blood  of  the 
human,  begins  with  the  introduction  of  spindle-shaped  sporozoites  in- 
jected into  the  circulation  with  the  bite  of  the  Anopheles  mosquito. 
Each  sporozoite  not  captured  by  phagocytes  at  once  bores  into  a  red 
cell,  where  it  quickly  goes  into  the  signet  ring  stage,  growing  rapidly  until 
the  corpuscle  is  more  or  less  filled  depending  upon  the  species  of  para- 
site, and  is  then  known  as  a  merocyte.  The  full-grown  merocyte  now 
divides  into  a  larger  or  smaller  number  of  bodies  (also  depending  upon 
the  species)  which  are  then  liberated,  being  now  free  in  the  plasma  and 


MOSQUITOES  AS  DISEASE   BEARERS 


109 


Fig.  91.  —  Diagram  to  show  life  history  of  parasite  {Plasmodium  prcecox)  of  sestivo-autumnal 
malaria.  1-6,  asexual  or  schizogonic  cycle  in  human  blood,  requiring  48  hours  to  com- 
plete (72  hours  in  quartan) ;  1,  represents  a  vermicule  or  sporozoite,  either  in  salivary 
gland  of  mosquito  or  newly  injected  into  human  circulation ;  2,  represents  a  red  blood 
corpuscle  about  to  be  parasitized  by  a  sporozoite  ;  .3,  shows  a  young  parasite  in  signet 
ring  form  ;  4,  fully  grown  parasite  with  dividing  nucleus  ;  5,  shows  parasite  sporulated, 
but  still  intracorpuscular ;  6,  sporulation,  each  body  a  merozoite  ready  to  enter  a  new 
corpuscle  ;  some  are  sexual  and  may  develop  into  gametes  ;  7a,  female  gametocyte,  still 
intracorpuscular  ;  7b,  male  gametocyte,  also  intracorpuscular ;  8a,  free  female  crescent, 
which  may  sporulate,  producing  a  parthenogenetic  cycle  (w,  x,  y,  z) ;  Sh,  male  gametocyte 
or.hyaline  crescent  (crescents  do  not  ordinarily  appear  in  the  blood  until  ten  days  or  more 
after  infection)  ;  9-20  illustrates  the  sporogonic  or  sexual  cycle  of  the  parasite  within  the 
body  of  a  female  Anopheline  mosquito,  requiring  six  to  ten  days  and  over  to  complete  ; 
9a,  95,  female  and  male  gametocytes  in  stomach  cavitv  of  mosquito  ;  10a,  female  gamete 
(macrogamete)  ;  106,  exflagellated  male  gametocyte;  11,  deflagellated  male  gamete 
(microgamete)  ;  12,  fertilization  ;  (9-13  requires  about  24  hours.)  13,  ookinete  or  zygote 
ready  to  penetrate  stomach  ;  14,  ookinete  burrowing  through  stomach  wall ;  15,  ookinete 
outside  of  stomach  wall  and  inside  peritoneal  lining,  forming  characteristic  cyst,  growing 
progressively  larger.  (16-19)  in  which  the  parasite  sporulates,  forming  the  sporozoites ; 
20  shows  sporozoites  (vermicules)  escaping  from  cyst  and  migrating  forward  to  salivary 
glands  (21)  ;  (14-20  requires  five|days  or  more.)  21,  salivary  glands  of  female  mosquito ; 
22,  head  of  female  Anopheles.  (Original,  with  suggestions  from  Grassi  and  Schaudinn 
in  Mense's  Handbuch.) 


110        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

are  known  as  merozoites.  The  time  required  for  this  sporulation  is  from 
twenty-four  to  seventy-two  hours  accofding  to  the  species.  Each  mero- 
zoite  now  enters  another  adjacent  red  cell  and  again  the  cycle  repeats 
until  the  infection  is  great  enough  to  produce  a  paroxysm,  i.e.  in  from 
six  to  twelve  days,  commonly  about  ten  days. 

The  great  majority  of  the  merozoites  are  asexual,  but  some  of  them 
are  potential  males  and  females,  which  require  a  longer  time,  probably 
not  less  than  ten  days,  to  develop  to  their  full  growth,  then  known  as 
gametocytes.  In  Plasmodium  vivax,  the  sexual  forms  are  not  easily  recog- 
nized ;  however,  the  following  characters  are  useful :  "  (1)  their  larger 
size,  (2)  more  abundant  pigment,  (3)  there  is  usually  only  one  fairly  large 
chromatin  mass,  whereas  in  an  asexual  form  of  nearly  equal  size  the 
chromatin  has  already  begun  to  divide  into  several  portions  (segment- 
ing stage)  "  (Stephens  and  Christophers).  In  P.  praecox  the  sexual 
individuals  are  in  the  form  of  crescents.  The  female  crescent  {macro- 
gametocyte)  has  the  pigment  collected  at  the  center  (Fig.  89e),  while  the 
male  crescent  (microgametocyte)  has  the  pigment  scattered  throughout 
and  is  known  as  a  hyaline  crescent  (Fig.  89/). 

With  the  complete  development  of  the  gametocytes  all  is  ready  for 
the  next  cycle  (the  sexual)  which  can  only  be  undergone  within  the  body 
of  an  Anopheline  mosquito.  In  the  meantime  the  asexual  cj'cle  is 
repeated  over  and  over,  unless  quinine  is  taken  to  destroy  the  parasites, 
or  until  senescence  occurs.  The  gametocytes  are  not  thus  easily  de- 
stroyed, persisting  in  the  body  for  long  periods  of  time,  and  may,  under 
certain  conditions,  result  in  relapses,  without  reinfection  by  mosquitoes, 
which  relapse  is  traceable  to  a  parthenogenetic  cycle  of  the  female 
(Fig.  91  w,  X,  y,  z).  But  for  this  phenomenon,  which  may,  of  course, 
fail  to  occur,  a  person  eventually  becomes  rid  of  malaria,  provided  he 
avoids  reinfection  by  mosquitoes  through  removal  from  a  malarial  lo- 
cality, because  of  the  senescence  which  naturally  results  from  continued 
sporulation  without  sexual  intervention  or  rejuvenation  in  the  mosquito. 
It  is  believed  that  this  senescence  or  eventual  dying  off  of  the  non-sexual 
forms  is  due  to  the  toxin  produced  by  these  organisms  reacting  upon 
themselves. 

Hence  it  becomes  clear  that  the  sexual  cycle  is  necessary  to  the  life 
of  the  species.  It  is  a  well-known  fact  that  the  male  gametocyte  extrudes 
flagella  when  malarial  blood  is  exposed  to  the  air,  as  when  in  contact 
with  a  glass  slide.  The  parasites  when  thus  taken  from  their  normal 
habitat  invariably  die  within  a  few  minutes,  unless  a  special  medium 
is  employed ;  e.g.  that  devised  by  Bass  in  which  the  asexual  cycle 
may  be  observed  outside  the  human  body. 

Sexual  development,  the  cycle  of  Ross  (Fig.  91,  9-22)  has  only 
been  observed  in  the  female  Anopheline  mosquito ;  in  the  stomach  of 
this  insect  flagellation  of  the  male  gametocyte  takes  place.  After  a 
peripheral  arrangement  of  the  chromatin  (in  clumps  corresponding  to 
the  number  of  flagella)  there  are  extruded  from  three  to  six  long  slender 


MOSQUITOES   AS  DISEASE   BEARERS  111 

filaments  (flagella),  each  of  which  breaks  loose  from  the  parent  body 
(exflagellation) ,  forming  the  male  gamete  (microgamete)  corresponding 
in  function  to  the  spermatozoon  of  higher  animals.  The  female  game- 
tocyte,  now  known  as  the  macrogamete,  having  been  taken  into  the  stom- 
ach of  the  mosquito  with  the  microgametocytes  in  the  act  of  sucking 
blood,  now  also  undergoes  certain  changes,  becoming  rounded  or  oval 
in  form  with  the  chromatin  mass  centrally  located.  In  this  condition, 
still  in  the  stomach  of  the  mosquito,  the  microgamete  penetrates,  i.e. 
fertilizes  the  macrogamete,  producing  the  ookinete,  in  which  stage  the 
wall  of  the  stomach  is  penetrated  and  a  position  is  taken  up  just  beneath 
the  membrane  forming  the  outer  stomach  lining.  In  this  position  the 
parasite  grows  enormously,  forming  a  cyst  (Fig.  91, 15-19)  in  which  many 
nuclei  appear  in  from  four  to  five  days.  These  tiny  nucleated  bodies 
give  rise  to  hundreds  of  spindle-shaped  organisms  (sporozoites)  which  are 
in  from  twenty-four  to  forty-eight  hours  more  shed  into  the  body  cavity 
of  the  mosquito.  The  sporozoites  eventually  collect  in  the  salivary 
glands,  remaining  there  until  the  mosquito  bites  again,  when  many  of 
them  may  be  injected  with  the  saliva  into  the  wound.  The  time  re- 
quired for  the  completion  of  the  sexual  cycle  varies  from  seven  to  ten 
days  under  favorable  conditions,  i.e.  an  average  temperature  of  not  less 
than  60°  F.  Once  infected  the  mosquito  probably  remains  infected  for 
the  rest  of  its  life. 

With  the  introduction  of  the  sporozoites  into  the  blood  of  the  next 
victim  the  asexual  cycle  begins  as  already  explained. 

Time  Factor.  —  Although  there  are  some  localities  in  which  nearly 
all  the  inhabitants  are  infected  with  malaria,  newcomers  or  visitors  may 
or  may  not  soon  fall  a  prey  to  the  disease,  for  the  reason  that  not  more 
than  25  to  35  per  cent  of  the  Anopheles  mosquitoes  are  infected  during 
the  height  of  the  season  and  correspondingly  fewer  early  in  the  spring. 
This  is  dependent  upon  both  the  time  when  the  infected  person  and  the 
next  victim  are  bitten.  Obviously  the  mosquito  cannot  transmit  malaria 
when  there  is  none  present  to  be  transmitted  ;  again,  the  sexual  parasites 
(gametocytes)  must  be  in  the  peripheral  circulation  when  the  mosquito 
bites  the  infected  individual ;  and  again  after  the  mosquito  becomes  in- 
fected a  period  of  not  less  than  six  days  (possibly  five  in  benign  tertian, 
and  twelve  days  in  sestivo-autumnal)  must  elapse  before  a  new  victim 
can  be  inoculated,  i.e.  the  time  required  for  the  sexual  development  of 
the  parasite.  This  incubation  period  may  be  prolonged  through  reduced 
temperature,  with  apparently  no  development  in  low  temperatures 
(according  to  Manson  this  phase  of  the  malaria  parasite  requires  a 
"  sustained  average  temperature  of  at  least  60°  F.").  Thus  it  becomes 
evident  that  the  time  factor  plays  an  important  role  in  the  spread  of 
malaria. 

Is  Malaria  Inherited  by  Mosquitoes  ?  —  For  the  reason  that  malaria 
is  said  at  times  to  be  contracted  by  explorers  who  have  entered  unin- 
habited territory  it  is  believed  by  some  that  the  mosquitoes  of  said  ter- 


112        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

ritory  had  become  infected  perhaps  years  ago  and  that  the  parasite  has 
been  handed  down  from  generation  to  generation  from  the  female  to  the 
ovum,  ovum  to  larva  and  thus  through  the  mosquito  cycle.  The  fact 
that  Texas  fever  is  thus  inherited  and  infection  is  brought  about  by  the 
seed  tick  seems  to  lend  weight  to  the  argument.  To  test  this  matter 
larvae  of  Anopheles  quadrimacukitus  were  brought  by  the  writer  from  an 
intensely  malarial  district  to  Berkeley  and  the  adults  reared  from  these 
were  permitted  to  bite  healthy  students,  and  in  no  case  did  infection 
result. 

Knowing  the  life  history  of  the  parasite  it  would  be  more  reasonable 
to  assume  that  other  warm-blooded  animals  besides  man  harbor  the 
protozoon  during  its  asexual  cycle,  but  numerous  and  convincing 
experiments,  in  which  monkeys,  horses,  dogs,  cats,  rabbits,  pigeons, 
owls,  etc.,  also  frogs  and  turtles  w^ere  used,  negate  this  assumption. 

The  explanation  is  probably  to  be  found  in  the  fact  that  such  indi- 
viduals must  necessarily  pass  through  malarial  districts  while  on  their 
way  to  uninhabited  territory.  Infection  might  easily  result,  but  the 
malaria  symptoms  do  not  appear  until  the  destination  is  reached.  The 
time  factor  and  exposure,  no  doubt,  explain  the  phenomenon. 

Anopheline  Species  Concerned.  —  Although  no  Anopheline  mosquito 
should  be  trusted,  there  are  comparatively  few^  species  which  are  experi- 
mentally known  to  be  carriers  of  malaria.  Anopheles  quadrimaculatus 
Say  and  A.  crucians  Wied.  are  the  most  dangerous  North  American 
species.  While  ^4.  j^unctiijenjiis  Say  may  be  very  abundant  in  certain 
localities,  malaria  may  be  rare  or  absent.  Anopheles  maculipennis 
Meig.  is  the  most  important  European  species ;  A.  albiirianus  Wied. 
and  A.  (Cellia)  argyrotarsis  Rob.  are  the  most  important  species  for 
Central  America.  Moreover  it  has  been  found  that  not  all  species  of 
malaria  parasites  can  be  carried  equally  well  by  the  same  species  of 
Anopheles,  e.g.  A.  crucians  is  said  to  be  the  most  important  carrier  of 
sestivo-autumnal  fever  but  is  negative  to  other  forms. 

Several  other  genera  of  Anopheline  mosquitoes  (Asiatic  and  African) 
include  malaria-bearing  species,  among' them  Cellia,  Nyssorhynchus, 
e.g.  N.  fuliginosus  Giles  of  India  and  the  Philippines,  Myzorhynchus, 
e.g.  M.  sinensis,  Wied.  of  China  and  the  Philippines,  and  Myzomyia, 
e.g.  Myzomyia  minimus  Theo.  of  the  Philippines.  The  aforementioned 
genera  are  all  to  be  included  in  the  genus  Anopheles. 

How  Does  the  Malaria  Parasite  Overwinter  ?  —  Since  malaria  has 
a  typical  seasonal  occurrence,  with  little  or  no  appearance  during  the 
winter  months,  the  question  arises,  does  the  parasite  overwinter  in  its 
human  host  to  break  out  in  the  spring  in  individual  cases  by  the  process 
of  parthenogenesis,  or  does  it  overwinter  in  the  body  of  the  mosquito? 
The  weight  of  evidence  is  against  the  latter  possibility.  The  writer 
believes  that  the  Anopheles  mosquito  seldom  or  ever  takes  a  suck  of 
blood  before  going  into  hibernation.  A  suck  of  blood  would  militate 
against  the  life  of  the  mosquito  inasmuch  as  it  causes  the  development 


MOSQUITOES  AS   DISEASE   BEARERS  113 

and  ultimate  extrusion  of  ova  and  that  terminates  the  life  of  the  insect. 
Other  physiological  reasons  involving  further  increased  metabolism  seem 
to  discount  the  possibility  of  successful  hibernation.  Furthermore  the 
writer  has  seen  great  numbers  of  voracious  Anopheles  in  the  spring  both 
indoors  and  out,  and  has  been  frequently  bitten  by  these  as  have  many 
others  without  becoming  infected.  These  hibernated  individuals  on 
coming  out  early  in  the  spring  bite  viciously  even  at  noonday.  Further- 
more evidence  that  infected  mosquitoes  exist  during  the  winter  months 
seems  to  be  lacking  or  has  been  overlooked. 

On  the  other  hand  latent  human  infection  has  been  amply  proved  and 
this  may  easily  lead  to  the  infection  of  the  mosquitoes  appearing  in  the 
early  spring  and  thus  lead  to  the  spread  of  malaria  as  the  season  advances. 

B,   Yellow  Fever 

Yellow  Fever.  —  Yellow  fever  is  a  disease  peculiarly  restricted  to  the 
tropics,  being  endemic  in  the  West  Indies,  spreading  thence  northward 
into  the  southern  United  States  and  westward  into  Panama,  central 
America,  Mexico,  the  west  coast  of  South  America  and  parts  of  Africa. 
The  disease  is  marked  by  a  rapidly  increasing  fever,  headache  and  back- 
ache, and  in  most  cases  followed  in  three  or  four  days  by  a  yellow  color- 
ing of  the  skin  (whence  the  specific  name)  and  a  characteristic  black 
vomit. 

A  Mosquito  the  Carrier.  —  Finlay  of  Havana  in  1881  was  the  first 
to  advance  the  mosquito  transmission  theory,  though  Nott  (according 
to  Nuttall)  as  early  as  1848  attributed  it  to  the  higher  insects.  Though 
the  former  carried  on  what  is  now  known  to  have  been  incriminating 
experiments  with  mosquitoes  on  non-immunes,  his  theory  was  discredited, 
until  Sternberg,  Surgeon  General  of  the  United  States  Army,  became 
interested  in  his  (Finlay's)  theory,  made  stronger  through  the  malaria 
discoveries,  and  established  a  commission  in  1900  to  study  the  yellow- 
fever-mosquito  theory  in  Cuba.  The  commission  consisted  of  Doctors 
Walter  Reed,  James  Carroll,  Jesse  W.  Lazear  and  Aristides  Agramonte, 
and  of  these  Doctors  Carroll  and  Lazear  contracted  the  disease  during 
the  progress  of  the  investigation,  the  latter  succumbing  to  the  attack. 
In  the  autumn  a  field  station  was  established  named  Camp  Lazear  in 
honor  of  the  deceased  investigator.  The  camp  was  systematically 
arranged  for  the  most  accurate  observations  and  experiments.  Two 
small  buildings  were  erected,  one  of  which  was  used  to  determine  whether 
yellow  fever  can  be  transmitted  through  contact  with  soiled  articles  of 
dress  and  bedding,  ventilation  being  purposely  poorly  provided  for,  the 
only  precaution  being  the  exclusion  of  mosquitoes.  The  second  building 
consisted  of  two  rooms,  with  thorough  ventilation  and  disinfection ;  one 
room  was  kept  free  from  mosquitoes,  while  into  the  other  were  intro- 
duced mosquitoes  which  had  previously  bitten  yellow  fever  patients.  In 
all  cases  the  individuals  experimented  on  were  non-immunes.     In  the 


114        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

first  case,  those  exposed  to  fomites,  none  became  infected,  though  the 
experiment  lasted  over  two  months.  In  the  second  case,  those  indi- 
viduals occupying  the  mosquito-protected  room  did  not  become  diseased, 
while  six  out  of  the  seven  occupying  the  room  into  which  mosquitoes  were 
introduced  became  ill  with  yellow  fever.  The  following  conclusions  were 
reached  by  the  commission  : 

"  1.  The  mosquito  —  C.fasciatus  (later  known  as  Stegomyia  calopus, 
now  jEdes  calopus)  serves  as  the  intermediary  host  for  the  parasite  of 
yellow  fever. 

2.  Yellow  fever  is  transmitted  to  the  non-immune  individual  by 
means  of  the  bite  of  the  mosquito  that  has  previously  fed  on  the  blood 
of  those  sick  with  this  disease. 

3.  An  interval  of  about  twelve  days  or  more  after  contamination 
appears  to  be  necessary  before  the  mosquito  is  capable  of  conveying  the 
infection. 

4.  The  bite  of  the  mosquito  at  an  earlier  period  after  contamina- 
tion does  not  appear  to  confer  any  immunity  against  a  subsequent 
attack. 

5.  Yellow  fever  can  also  be  experimentally  produced  by  the  sub- 
cutaneous injection  of  blood  taken  from  the  general  circulation  during 
the  first  and  second  days  of  this  disease. 

6.  An  attack  of  yellow  fever,  produced  by  the  bite  of  the  mosquito, 
confers  immunity  against  the  subsequent  injection  of  the  blood  of  an 
indi^ddual  suffering  from  the  non-experimental  form  of  this  disease. 

7.  The  period  of  incubation  in  thirteen  cases  of  experimental  yellow 
fever  has  varied  from  forty-one  hours  to  five  days  and  seventeen  hours. 

8.  Yellow  fever  is  not  conveyed  by  fomites,  and  hence  disinfection 
of  articles  of  clothing,  bedding,  or  merchandise,  supposedly  contami- 
nated by  contact  with  those  sick  with  this  disease,  is  unnecessary. 

9.  A  house  may  be  said  to  be  infected  with  yellow  fever  only  when 
there  are  present  within  its  walls  contaminated  mosquitoes  capable  of 
conveying  the  parasite  of  this  disease. 

10.  The  spread  of  yellow  fever  can  be  most  effectively  controlled  by 
measures  directed  to  the  destruction  of  mosquitoes  and  the  protection 
of  the  sick  against  the  bites  of  these  insects. 

11.  While  the  mode  of  propagation  of  yellow  fever  has  now  been 
definitely  determined,  the  specific  cause  of  this  disease  remains  to  be 
discovered." 

Etiology.  —  The  work  of  the  Yellow  Fever  Commission  proved 
beyond  doubt  that  the  causative  agent  of  yellow  fever  is  blood  inhabit- 
ing, is  a  filterable  virus  and  is  not  traceable  to  Bacillus  icteroides  of 
Sanarelli  (1897).  The  behavior  of  the  disease  indicates  that  it  is  of 
protozoal  nature,  perhaps  closely  related  to  malaria,  but  all  careful 
research  thus  far  put  forth  has  failed  to  reveal  an  organism.  Seidelin 
(1909)  believed  it  to  be  Paraplasma  fiavigenum,  but  this  is  strongly 
denied  bv  other  workers. 


MOSQUITOES  AS  DISEASE   BEARERS 


115 


Time  Factor.  —  Since  the  yellow  fever  mosquito  is  both  diurnal  and 
nocturnal  early  in  its  adult  history,  it  seems  that  the  virus  could  be, 
conveyed  at  any  time  of  the  day  or  night ;  this  is,  however,  not  true,  as 
evidenced  b}^  the  following  observations :  first,  a  lapse  of  at  least  twelve 
days  is  required  before  the  bite  of  the  mosquito  becomes  infective ; 
second,  after  once  having  fed  and  deposited  her  eggs  (three  days  later) 
the  mosquito  becomes  nocturnal  in  habit.  Therefore  the  day-flying 
individuals  are  too  young  to  harbor  the  infective  virus  of  yellow  fever. 

Another  important  factor  to  be  considered  is  that  the  Stegomyia  can 
only  become  infected  by  feeding  on  a  Yellow  Fever  patient  during  the 
first  three  days  of  his  sickness. 

As  in  malaria,  infective  blood  from  a  yellow  fever  patient  loses  its 
virulence  on  exposure  to  air,  —  "  virulent  blood  serum  lost  its  virulence 
in  forty-eight  hours,  if  exposed  to  the  air  at  24°  to  30°  C."  (Mar- 
choux  and  Simond). 

C.     FiLARIASIS 

Filariasis.  —  Filariasis  is  a  disease  of  the  lymphatic  system  pro- 
duced by  nematode  worms  of  the  genus  Filaria.  It  is  manifested  by  a 
swelling,  often  to  enormous  pro- 
portions, of  the  lower  extrem- 
ities, commonly  the  scrotum. 
In  its  more  pronounced  and 
advanced  stages  it  commonly 
causes  elephantiasis,  although 
in  this  stage  the  filarise  may 
not  be  present. 

Filariasis  and  elephantiasis 
are  comparatively  common  in 
the  tropics  and  occur  also  in 
certain  subtropical  regions ;  ac- 
cording to  Manson^  about  every 
second  individual  in  Samoa  is 
thus  afflicted. 

While  the  absence  of  spe- 
cific filarial  poisons,  which  might 
produce    the  disease,   has    not 
been  disproven,  it  is  said  that  the  swellings  are  produced  by  occlusion 
of  the  lymphatics  on  the  part  of  the  nematodes. 

The  Parasite.  —  Although  there  are  several  blood-inhabiting  worms 
belonging  to  the  family  Filariidse,  only  one  species  seems  to  be  of  any 
great  pathological  importance,  namely  Microfilaria  bancrofti  Cobbold 
{Filaria  sanguinis  hominis  Lewis),  a  tropical  and  subtropical  species. 

Microfilaria  bancrofti,  which  is  the  larval  form  of  Filaria  bancrofti, 
inhabits  the  blood  plasma,  is  a  very  slender  worm,  about  the  diameter 

1  Mauson,  Sir  Patrick,  1909  {loc.  cit.). 


Fig.  92.  —  Microfilaria  bancrofti,  in  human  blood. 
X  333. 


116        MEDICAL  AND  VETERINARY  ENTOMOLOGY 

of  a  red  blood  corpuscle  and  is  about  .3  ram.  in  length  (Fig.  92).  It  is 
inclosed  in  a  very  delicate  sheath  inside  of  which  the  worm  has  some 
latitude  of  motion  both  forward  and  backward.  It  is  known  that  this 
parasite  maintains  a  very  striking  periodicity,  being  abundant  in  the 
peripheral  circulation  only  at  night,  beginning  with  the  early  evening 
and  lasting  until  early  morning  with  the  greatest  abundance  at  mid- 
night, at  which  time  Manson  reports  that  "it  is  no  unusual  thing  to 
find  as  many  as  three  hundred,  or  even  six  hundred  in  every  drop  of 
blood."  During  the  day  filarise  are  found  in  the  lungs  and  large 
visceral  blood  vessels. 

The  adult  filarise,  which  are  slender  hair-like  worms,  inhabit  the 
lymphatic  ducts.  The  female  parasite  measures  from  85  to  90  mm.  in 
length  and  the  male  about  40  mm.  (Manson).  The  ovoviviparous 
females  extrude  myriads  of  larval  filarise  into  the  lymph  sinuses  which 
shortly  thereafter  swarm  into  the  blood  vessels,  occupying  the  lungs 
mainly  during  the  day  and  the  peripheral  vessels  by  night. 

The  Mosquito's  Role  in  Filariasis.  —  Manifestly  the  swarming  of 
thousands  upon  thousands  of  Microfilarise  in  the  peripheral  blood  at 
night  offers  the  very  best  opportunity  for  passage  into  the  body  of  noc- 
turnal blood-sucking  insects,  of  which  the  mosquito  stands  the  best 
chance,  owing  to  relative  abundance  and  habits.  The  Culicine  mosqui- 
toes for  some  reason  seem  to  be  the  most  important  instruments  of 
transmission,  particularly  Cidex  (fatigans)  quinquefasciatus  Say. 

Once  the  Microfilarise  are  in  the  stomach  of  the  mosquito  these  burst 
themselves  free  from  their  enclosing  sheaths  and  proceed  to  migrate  to 
the  thoracic  muscles,  wdiere  a  definite  metamorphosis  is  undergone, 
resulting  in  a  great  increase  in  size,  and  the  formation  of  a  mouth  and 
alimentary  tract  (Manson).  This  metamorphosis  requires  from  sixteen 
to  twenty  days,  depending  on  the  temperature  as  do  other  mosquito- 
borne  parasites.  From  this  position  the  worms  work  their  way  into 
the  ventral  portions  of  the  head  and  the  proboscis  inside  the  labium. 
From  this  point  they  enter  the  wound  produced  when  the  mosquito 
pierces  the  skin  of  its  victim.  Apparently  the  filarise  burrow  directly 
through  the  membranous  portion  of  the  labella  at  the  point  of  attach- 
ment to  the  labium.  From  the  peripheral  system  the  nematodes  soon 
find  their  way  into  the  lymphatics  where  sexual  maturity  occurs. 

Culex  {fatigans  Wiedem.)  quinquefasciatus  Say  is  one  of  the 
most  abundant  and  widely  distributed  species  of  Culicine  mosquitoes 
of  the  tropics  and  subtropics.  It  is  a  comparatively  small  species 
(about  5  mm.)  and  is  uniformly  brown,  varying  from  light  to  dark,  in 
color.  On  the  thorax  there  are  situated  two  narrow  median  indistinct 
longitudinal  lines.  Apparently  any  stagnant  fresh  water,  from  the 
clearest  to  the, vilest,  aft'ords  a  good  breeding  place  for  Culex  quinqne- 
fasciatus.     Stagnant,  filthy  gutter  water  seems  to  be  especially  favorable. 

The  entire  life  history,  from  egg  to  imago,  is  completed  in  about  ten 
days  under  optimum  conditions. 


MOSQUITOES  AS  DISEASE   BEARERS  117 

D.  Dengue 

Dengue,  or  Breakbone  Fever,  an  epidemic,  infectious,  influenza-like 
disease  of  the  tropics  and  subtropics,  breaks  out  suddenly  as  an  acute 
fever  with  "  eruption  and  peculiarly  severe  rheumatic-like  pains  in  the 
joints  and  limbs  .  .  .  not  accompanied  by  pulmonary  and  other  serious 
complications  "  (Manson),     The  disease  is  benign  and  of  short  duration. 

It  is  caused  by  a  filterable  virus  which  is  blood-inhabiting  like  yel- 
low fever.     The  incubation  period  is  said  to  be  from  two  to  five  days. 

How  Transmitted.  —  Sufficient  evidence,  both  experimental  and 
circumstantial,  is  at  hand  to  incriminate  mosquitoes,  notably  Culex 
quinquefasciatus  and  .Edes  calopus ;  and  at  least  one  reputable  phy- 
sician has  told  the  writer  that  the  control  of  mosquitoes  during  a  cer- 
tain dengue  epidemic  in  the  Philippines  resulted  in  the  control  of  the 
disease.  Whether  or  not  there  were  other  factors  of  importance  in- 
volved is,  of  course,  a  question. 

E.  Verruga 

Verruga  (Verruca  peruana),  Carrion's  disease  or  oroya  fever, 
occurs  endemically  in  certain  high  altitudes  in  Peru.  According  to 
Giltner  ^  the  disease  is  characterized  by  fever,  rheumatoid  pains,  anaemia 
and  an  eruption  which  develops  into  bleeding,  warty  tumors.  It  is  an 
infectious  disease  of  ancient  origin  attacking  persons  of  both  sexes  and 
all  ages.  The  mortality  is  very  high  in  the  malignant  form,  while  in  the 
benign  form  the  mortality  is  low.  The  incubation  period  is  from 
one  to  three  weeks. 

Causative  Organism.  —  The  causative  organism  of  verruga  has  not 
been  discovered  ;  however,  characteristic  intracorpuscular  bodies  are 
present,  at  first  believed  to  be  parasites,  and  so  described  in  the  Verruga 
Expedition  Report.^  These  bodies  are  known  as  "  Bartonia  bodies," 
or  X-bodies,  and  are  described  as  follows  : 

"  Bartonia  bacilUformis.  Gen.  et  sp.  nov.  Parasites  consisting  of 
rounded  or  oval  forms  or  of  slender  straight,  curved  or  bent  rods  occur- 
ring either  singly  or  in  groups,  but  characteristically  in  chains  of  several 
segmenting  organisms,  sometimes  swollen  at  one  or  both  ends  and  fre- 
quently beaded.  Reproduction  occurs  by  binary  division.  Endowed 
with  independent  motility,  moving  in  the  direction  of  the  long  diameter, 
living  within  the  red  blood  corpuscles  of  man  and  producing  a  grave 
form  of  anaemia  known  in  Peru  as  Oroya  fever.  Stained  preparations 
suggest  differentiation  of  cytoplasm  and  nuclear  material." 

1  Giltner,  H.  A.,  1911.  Verruca  peruana  or  Carrion's  disease.  Journ. 
Amer.  Med.  Assoc,  Dec.  23,  1911. 

2  Strong,  R.  P.,  Tyzzer,  E.  E.,Brues,  Charles  T.,  Sellards,  A.  W.,  Gastiaburn, 
J.  C,  1913.  Verruga  peruviana,  Oroya  fever  and  Uta,  preliminary  report  of 
the  first  expedition  to  South  America  from  the  department  of  Tropical  Medi- 
cine of  Harvard  University.     Journ.  Amer.  Med.  Asso.,  Vol.  LXI,  No.  19. 


118        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

Mode  of  Transmission.  —  The  first  experimental  transmission  of 
verruga  was  accomplished  by  Townsend  ^  in  Peru,  the  agent  having 
been  Phlebotomus  verrucarum  (Townsend)  and  the  animal  experimented 
on  was  a  hairless  dog.  The  incubation  period  in  this  animal  was  about 
six  days,  i.e.  on  July  11,  1913,  1  cc.  "  of  artificial  serum  containing  the 
triturated  bodies  of  twenty  females  of  the  Phlebotomus,  collected  on  the 
night  of  July  9-10  in  Verruga  Canyon  "  was  injected  subcutaneously 


Fig.  93.  —  Phlebotomus  or  sand  fly  (male,  left ;  female,  right).     Carrier  of  three-day  fever 
Other  species  transmit  Papatici  fever  and  Verruga.       X  8. 


in  the  right  shoulder  of  the  dog,  and  on  July  17  the  typical  eruption  be- 
gan to  appear. 

The  same  author  ^  later  reports  a  human  case  in  which  the  infec- 
tion was  undoubtedly  introduced  by  the  bites  of  Phlebotomus  ("  fifty- 
five  unmistakable  Phlebotomus  bites  on  the  backs  of  his  hands  and 
wrists")  received  September  17,  1913,  X-bodies  appearing  October  1, 
but  "  no  clinical  symptoms  other  than  a  headache  or  slight  feverishness 
at  times,  until  October  25,  when  a  decided  rise  of  temperature  occurred 
and  the  X-bodies  were  found  to  be  much  increased  in  number." 

Phlebotomus  Flies.  —  The  Phlebotomus  flies  (Fig.  93)  belong  to  the 
family  Psychodidse  of  the  order  Diptera,  commonly  known  as  "  owl 

1  Townsend,  Charles  H.  T.,  1913.  The  Transmission  of  Verruga  by  Phle- 
botomus.    Journ.  Amer.  Med.  Assoc,  Vol.  XIV,  No.  19. 

2  Townsend,  Charles  H.  T.,  1913.  Human  case  of  Verruga  directly  trace- 
able to  Phlebotomus  verrucarum.     Entomological  News,  Vol.  XXV,  No.  1. 


MOSQUITOES  AS  DISEASE   BEARERS  119 

midges,"  thickly  haired  moth-like  flies  of  small  size  (3-4  mm.  long). 
The  wings  are  ovate  in  shape  with  heavy,  almost  exclusively  longitudi- 
nal veins.  The  wings  are  densely  hairy  and  fold  roof-like  over  the 
abdomen.  The  habits  of  the  Phlebotomus  flies  are  described  by  several 
authors,  among  them  Townsend,^  who  says  that  the  tiny  blood-sucking 
gnats  "  avoid  wind  and  sun  and  full  daylight.  They  appear  only  after 
sunset,  and  only  then  in  the  absence  of  wind.  They  enter  dwellings  if 
not  too  brightly  lighted,  but  are  not  natural  frequenters  of  human 
habitations.  They  breed  in  caves,  rock  interstices,  stone  embankments, 
walls,  even  in  excavated  rock  and  earth  materials.  .  .  .  They  hide  by 
day  in  similar  places  or  in  shelter  of  rank  vegetation.  Deep  canyons, 
free  from  wind  and  dimly  lighted,  are  especially  adapted  to  them.  Thick 
vegetation  protects  them  from  what  wind  there  is  by  day  or  night. 
,  .  .  The  flies  suck  the  blood  of  almost  any  warm-blooded  animal,  and 
even  that  of  lizards  in  at  least  one  known  case.  Thus  they  are  quite 
independent  of  man,  and  this  accords  with  the  verruga  reservoir  being 
located  in  the  native  fauna." 

The  life  history  of  Phlebotomus  papatasii  (related  to  "  Papatici 
Fever,"  a  benign  dengue-like  disease)  is  said  by  Marett  ^  to  require 
about  three  months,  —  egg  stage,  six  to  nine  days ;  larval  stage,  about 
eight  weeks ;   and  pupal  stage,  from  eleven  to  sixteen  days. 

Marett  also  suggests  the  following  prophylactic  measures,  viz. : 
"  facing  of  walls,  the  remo\'al  of  heaps  of  stones  and  the  blocking  of  all 
holes  which  might  serve  as  shelter  places  for  the  flies  ;  also  covering  the 
ventilators  with  fine-meshed  wire  gauze,  and  the  cleaning  of  all  rough, 
made  ground  from  weeds,  so  that  all  holes  may  be  discovered  and  filled 
up  with  beaten  earth.  The  encouragement  of  gardening  on  such  grounds 
is,  he  thinks,  also  desirable.  Large  embankments  should  be  planted 
with  native  aromatic  plants  such  as  thyme,  pennyroyal,  etc.,  and  kept 
well  earthed." 

1  Townsend,  Charles  H.  T.,  1913.  A  Phlebotomus,  the  practically  certain 
carrier  of  verruga.     Science,  N.  S.,  Vol.  XXXVIII,  No.  971. 

2  Marett,  Capt.  P.  J.,  1913.  The  Phlebotomus  Flies  of  the  Maltese 
Islands.  R.  A.  M.  C.  Journ.  XX,  No.  2,  pp.  162-171.  (Abstract  in  The 
Review  of  Applied  Entomology,  Vol.  1,  Ser.  B.  Part  2,  pp.  27-29.) 


CHAPTER   XI 
MOSQUITO   CONTROL 

Where  Mosquitoes  Breed.  —  As  has  already  been  pointed  out,  water 
is  absolutely  essential  for  mosquito  breeding,  though  the  situation  varies 
somewhat  for  the  species.  Places  suitable  for  Culicine  mosquitoes  are 
not  always  suitable  for  the  Anopheles,  but  generally  where  the  latter  is 
found  the  former  may  also  occur.  The  Culicine  female  will  deposit  her 
eggs  even  in  the  smallest  receptacles  containing  water,  such  as  broken 
gourds,  tin  cans,  tubs,  barrels,  etc.  (Fig.  94) .     It  should  be  noted  here 


Fig.  94.  —  Tin  cans,  tubs  and  barrels  in  which  water  may  stand  and  breed  mosquitoes. 

that  running  water  is  not  a  favorable  breeding  place  for  se^'eral  obvious 
reasons  illustrated  in  the  life  history  already  discussed.  However,  a 
running  stream  should  be  "  edged  up  "  so  that  no  little  coves  are  formed 
in  which  the  water  remains  comparatively  quiet.  This  applies  also  to 
gutters  (Fig.  95)  and  irrigation  ditches. 

The  most  favorable  places  for  the  propagation  of  Anopheles  are 
overflowed  areas  in  which  the  water  is  shallow  enough  to  allow  grass  and 
•other  low  vegetation  to  be  barely  covered  or  slightly  protruding  (Fig. 
96)  ;  such  conditions  are  often  produced  by  breaks  in  irrigation  ditches, 
leaking  water  supply  pipes,  "  leaky  "  hydrants  (Fig.  97)  and  improperly 
channeled  creeks.  Marshy  areas,  in  which  the  water  is  just  below  the 
surface,  are  made  dangerous  through  the  hoof  marks  of  cattle  and  horses 
The  writer  has  found  that  places,  which  the  casual  observer  considers 
highly  dangerous,  are  often  quite  harmless.  Reservoirs,  dredger  ponds, 
and  sluggish  streams  are  often  regarded  with  the  keenest  disfavor, 
though  examination  may  indicate  the  entire  absence  of  larvae.  A 
badly  kept  basin  or  reservoir  may,  however,  prove  a  menace  due  to  the 

120 


MOSQUITO  CONTROL 


121 


growth  of  vegetation  along  the  edges  and  to  the  shallow  condition  of  the 

water.    A  clean  pond  with  sharp,  deeply  cut  banks  need  not  be  a  menace 

as  a  mosquito  breeder, 

especially  when  stocked 

with  surface-feeding 

fishes. 

A  receding  stream 

(Fig.    98)    often    leaves 

shallow  ponds  along  its 

banks.     These  very  fre- 
quently become  most 

suitable  breeding  places 

for  mosquitoes,  especially 

Anopheles.     The    con- 
struction of  railroads  and 

highways    frequently 

results  in    obstructing 

natural    drainage,    thus 

causing  water  to  stand. 
It  would  hardly  seem 

possible  for  wrigglers  to 
develop  in  soap  and  lye 
laden  pools  from  laun- 
dries, but  such  is  never- 
theless   frequently     the 
case,  even  for  Anopheles. 
Cesspools   also  often 
prove  a  serious  menace. 
Essentials  of  Control. 
—  In  our  study  of  the 
life  history  of  the  mos- 
quito we  have  seen  that 
standing    water    (or    at 
least  very  sluggish  water) 
is    absolutely   necessary 
for   the  propagation   of 
mosquitoes;  therefore,  the  essentials  of  control  are  at  once   evident, 
namely,  the  drainage  of  the  water  or  its  protection  mechanically  to 
prevent  the  adult  female  from  depositing  her  eggs  thereon  or  the  appli- 
cation of  chemicals  to  destroy  the  larvae  and  pupse.    Manifestly  this 
calls  for  either  temporary  or  permanent  control.     Temporary  control 
consists  in  the  application  of  some  insecticide  to  the  water,  such  as 
kerosene,  nicotine,  phinotas  oil  or  salt  (in  the  case  of  fresh-water  species 
under  certain  conditions) .     This  method  requires  more  or  less  constant 
repetition,  and  involves  repeated  expenditure  of  time,  labor  and  money, 
but  is  extremely  useful  and  really  essential  during  the  time  that  the  per- 


FiG.  95. 


Stagnant  water  in  gutters  breeds  numerous 
mosquitoes,  often  Anopheles. 


122        MEDICAL  AND   VETERINARY  ENTOMOLOGY 


manent  work  is  being  advanced,  in  that  wrigglers  and  tumblers,  which 
have  already  made  their  appearance,  are  destroyed. 

For  the  permanent  control  of  mosquitoes,  especially  the  Anopheles, 
the  best  method,  by  all  odds,  is  drainage,  correction  of  irrigation  defects, 
cutting  deeper  channels  where  the  water  spreads,  etc.  Thirty  minutes' 
labor  in  cutting  a  ditch  deeper,  or  digging  a  new  one  for  a  short  distance, 

has  very  often  elim- 
inated a  nuisance  that 
has  bred  malaria  mos- 
quitoes season  after 
season. 

It  is  highly  im- 
portant that  control 
efforts  should  be  sys- 
tematic and  thorough. 
Haphazard,  slipshod 
work  only  results  in  dis- 
satisfaction and  new 
crops  of  mosquitoes. 
Oiling  Methods. 
—  As  has  already 
been  explained,  mos- 
quito wrigglers  and 
tumblers  must  come 
to  the  surface  of  the 
water  for  air,  hence 
any  material  that  will 
form  an  effective  film 
over  the  surface  of  the 
water  will  serve  to 
suffocate  them.  For 
this  purpose  kerosene 
has  been  found  to  be 
the  cheapest  and  at 
the  same  time  most  available  material.  After  a  coat  of  oil  has  been  ap- 
plied the  pre\'iously  disturbed  wrigglers  and  tumblers  may  be  seen  to  rise 
and  touch  the  under  side  of  the  oil  film  and  successively  try  place  after 
place  for  a  point  of  emergence.  Death  from  suft'ocation  follows  in  from 
three  to  fifteen  minutes.  The  same  results  can  be  secured  by  placing 
wrigglers  and  tumblers  in  a  vessel  of  water  and  agitating  violently  for  a 
few^  minutes  so  that  the  insects  cannot  come  to  the  surface  to  breathe. 
Kind  of  Oil.  —  The  most  desirable  oil  for  mosquito  control  is  one 
that  will  spread  most  readily  without  breaking  up  into  patches  and  that 
will  remain  on  the  water  for  the  longest  time  in  an  eft'ective  condition. 
Crude  oil,  it  will  be  seen,  breaks  up  into  patches  between  which  the  water 
is  not  affected.     Wrigglers  have  been  found  by  the  writer  developing  in 


Fig.  96.  —  An  ideal  Anopheles  breeding  place.  The  water 
is  shallow  and  clear,  with  much  vegetation.  Also 
.shows  use  of  knapsack  spray  pump. 


MOSQUITO   CONTROL 


123 


such  situations  in  localities  where  oil  had  been  applied  liberally.  Sev- 
eral very  prominent  fiascos  have  been  made  in  attempting  thus  to 
control  mosquitoes.  Crude  oil  furthermore  cannot  be  used  well  in  ordi- 
nary spray  pumps.  The  lasting  quality  is,  however,  very  good.  Kero- 
sene spreads  most  satisfactorily  and  does  its  work  quickly,  but  evaporates 
in  a  comparatively  short  time,  thus  requiring  frequent  repetition.  A 
mixture  of  the  two  can  very  well  be  made  which  will  bring  about 
more  nearly  the  desired  results.  Our  best  results  have  been  obtained 
with  a  mixture  of  approximately 
equal  parts  of  crude  oil  and  kero- 
sene, though  the  proportion  may  per- 
haps safely  range  to  three  parts  of 
the  former  to  one  of  the  latter.  We 
have  also  used  successfully  a  treated 
stove  oil  of  about  28°  Beaume. 

Oil  purchased  on  the  market  as 
"  crude  oil  "  varies  from  12°  to  18° 
Beaume,  while  "  stove  distillate  " 
varies  from  28°  to  32°,  and  water- 
white  kerosene  from  40°  to  42°. 
Knowing  the  specific  gravity  of  the 
oil  purchased,  it  can  easily  be  cal- 
culated how  to  mix  with  lighter  or 
heavier  oil  in  order  to  obtain  the 
required  consistency.  Thus  if 
kerosene  (42°)  is  at  hand  and  crude 
oil  ( 1 5°) ,  use  about  ten  gallons  of  the 
former  to  twelve  gallons  of  the  latter. 
For  spring  and  autumn,  28°  to  30° 
Beaume  is  to  be  recommended, 
while  for  summer  use  a  heavier  oil 
at  about  26°  is  preferable.  To  mix 
the  oils  it  is  necessary  to  use  the 
spray  pump,  i.e.  repeatedly  fill  the  chamber  with  oil  in  proper  propor- 
tions, introducing  the  nozzle  end  of  the  hose,  and  churn  a  few  minutes. 

How  to  Apply  Oil.  —  Simply  pouring  on  the  oil  with  a  dipper  is 
wasteful  and  requires  some  little  time  if  all  the  smaller  adjacent 
pools  of  water  are  to  be  treated.  Experience  has  taught  that  the 
small,  apparently  insignificant  pools  of  water  are  in  reality  the 
greatest  menace  and  are  commonly  overlooked.  The  use  of  a  knap- 
sack spray  pump  (Figs.  96  and  99)  of  five-gallon  capacity  is  highly 
recommended.  This  can  be  strapped  on  the  back  and  will  provide 
enough  oil  for  twenty  minutes'  continuous  spraying  or  one  or  two 
hours  of  ordinary  oiling.  Where  it  is  out  of  the  question  to  use  a  horse 
and  cart  to  carry  the  oil,  the  field  man  can  save  himself  many  steps  and 
some  embarrassment  if  he  will  make  it  a  habit  to  carry  a  small  quantity 


Fig.  97.  —  The  leaking  faucet  with  the  re- 
sulting pool  of  water  is  often  a  constant 
menace  in  the  entire  absence  of  other 
mosquito-breeding  .source-s. 


124        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

of  oil  with  him  at  all  times  in  a  pint  or  quart  tin  to  which  is  attached  a 
rubber  bulb  and  a  spray  spout.     The  inspector  usually  devotes  a  day  or 


Fig.   98.  —  Receding  streams  leave  pools  of   standing  water   along  the  banks,  in  which 
mosquitoes  may  breed  plentifully. 


two  to  inspection  and  follows  this  with  an  entire  day  of  oiling  and  he  may 
then  need  to  use  a  good  many  gallons  of  oil  in  a  few  hours.     A  good-sized 


Fig.  99.  — •  Showing  use  of  knapsack  spray  pump  in  mosquito  control. 


MOSQUITO   CONTROL  125 

wad  of  cotton  waste  soaked  in  oil  and  placed  in  a  pool  of  stagnant  water 
will  continue  to  give  off  oil  for  some  time  and  is  often  very  serviceable. 

When  to  Apply  Oil,  —  Oil  should  be  applied  whenever  and  wherever 
the  wrigglers  and  tumblers  are  found,  even  though  permanent  correction 
is  planned.  This  will  prevent  them  from  being  washed  out  into  some 
other  situation  where  they  would  be  liable  t:)  complete  their  transforma- 
tion. The  frequency  with  which  oil  must  be  applied  depends  on  the 
rate  of  development  of  the  wrigglers  and  the  evaporation  of  the  oil,  — • 
both  conditions  being  dependent  on  the  temperature.  Therefore,  more 
frequent  applications  are  necessary  during  midsummer,  when  with  the 
oil  mentioned  above,  spraying  should  be  repeated  at  least  every  twelve 
days,  and  under  cooler  conditions  (averaging  50°  to  60°  F.)  every  three 
weeks.  If  it  requires  only  ten  days  for  some  mosquitoes  to  pass  through 
their  entire  transformation,  one  might  think  that  applications  of  oil 
every  twelve  days  would  not  be  often  enough,  but  it  must  be  remem- 
bered that  the  oil  kills  all  wrigglers  and  tumblers  at  the  time  of  contact 
and  the  film  remains  on  the  water  for  about  two  days,  sometimes  longer, 
during  which  time  any  adult  mosquito,  intending  to  lay  eggs,  is  killed 
on  coming  in  contact  with  the  oil.  After  the  oil  has  evaporated  quite 
largely,  the  breeding  may  begin  again,  but  the  next  application  of  oil 
will  catch  the  oncoming  brood  before  the  ten  days  necessary  for  com- 
plete development  have  expired. 

Copper  Sulphate.  —  Treating  water  with  copper  sulphate  (CUSO4) 
for  the  destruction  of  mosquito  larvae  and  pupse  has  been  proved  ineffec- 
tive, but  it  is  nevertheless  useful  in  cases  where  stagnant  water  is  cov- 
ered so  badly  with  algae  as  to  retard  the  effect  of  insecticides.  The  writer 
has  invariably  had  better  results  with  oil  applied  to  algse-covered  ponds 
after  liberal  treatment  with  copper  sulphate,  than  when  the  latter  was 
not  applied.  The  same  also  held  true  for  soapy  laundry  pools  which  have 
frequently  been  found  to  harbor  abundant  Anopheles  larvae.  Copper 
sulphate  is  ordinarily  used  not  in  excess  of  one  part  per  million  of  water. 

Tobacco  Decoctions.  —  The  writer  has  thoroughly  tested  the  eflB- 
ciency  of  tobacco  decoction,  both  in  the  laboratory  and  in  the  field,  and 
has  found  it  very  effective,  but  the  expense  is  prohibitive  when  it  is  used 
on  a  large  scale.  Sulphate  of  nicotine  (Black  leaf  40)  made  by  the 
Kentucky  Tobacco  Products  Company,  was  found  to  effectively  de- 
stroy all  wrigglers  and  tumblers  when  used  in  the  ratio  of  1  part  to  750 
parts  of  water.  Greater  dilution  proved  uncertain  for  the  pupae,  but 
1  to  1000  is  still  effective  for  larvae.  In  field  work  this  material  was 
effectively  used  on  smaller  pools  and  also  on  a  good-sized  quarry-hole 
pond,  but  the  cost  proved  too  great.  Ordinary  "  Black  leaf  "  tobacco 
decoction  cannot  be  used  effectively  in  a  greater  dilution  than  1  part 
to  20  of  water.  It  must  be  remembered  in  all  cases  that  a  material  in 
weaker  strengths  would  be  just  as  useful  and  less  expensive  provided 
it  killed  the  insect,  even  after  a  day  or  two,  and  this  factor  was  borne  in 
mind  during  the  progress  of  experimentation. 


126        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

Smith  found  that  "  Nicofume  "  destroys  all  small  wrigglers  at  the 
rate  of  1  part  in  2500  parts  of  water,  and  all  wrigglers  and  eventually  all 
tumblers  at  the  rate  of  1  part  to  1500  parts  of  water.  Rapid  destruction 
was  accomplished  by  using  1  part  of  "  Nicofume  "  to  750  parts  of  water. 

Other  Larvaecides. — Many  chemicals  have  been  used  experimentally 
against  mosquito  larvae  with  more  or  less  success,  but  in  most  cases 
either  the  cost  or  danger  to  life  is  forbidding,  leaving  oil  still  the  sim- 
plest and  cheapest  remedy.  Among  the  more  effective  remedies  may  be 
mentioned  "  Chloronaptholeum  "  used  as  a  spray  especially  in  cess- 
pools and  other  unsanitary  situations ;  Phinotas  oil  acts  quickly  as  a 
poison  even  at  very  low  concentrations,  but  should  not  be  used  where 
there  is  danger  of  poisoning.  The  simple  addition  of  lime  or  chloride 
of  lime  to  damp  places  with  just  enough  water  present  to  breed  mos- 
quitoes proves  quite  advantageous. 

The  writer's  enthusiasm  to  carry  on  extensive  experimentation  with 
larvaecides,  except  as  already  noted,  has  never  been  full}'  worked  up, 
owing  to  the  fact  that  such  materials  are  too  often  taken  as  an  excuse  for 
the  more  satisfactory  permanent  methods.  The  general  public  desires 
above  all  things  a  kind  of  magic  remedy  to  be  applied  once  with  little 
trouble  and  permanent  relief,  whether  the  appearance  of  things  has  been 
improved  or  damaged,  it  matters  not. 

The  use  of  larvaecides  has,  however,  a  very  important  place  in  the 
crusade  against  the  mosquito,  and  until  communities,  whether  large  or 
small,  learn  to  appreciate  the  advantage  attained  by  proper  drainage 
facilities  and  careful  attention  to  prevent  water  from  becoming  stagnant, 
both  early  and  late  in  the  year,  these  materials  must  be  used. 

At  the  beginning  of  a  campaign,  when  larvae  and  especially  pupae  are 
already  present,  a  good  larvaecide  must  be  applied  until  proper  drainage 
is  secured. 

"Larvicide,"  generally  used  in  the  Panama  Canal  Zone,  is  prepared 
from  crude  carbolic  acid.  Its  manufacture  and  method  of  application 
are  fully  described  in  an  article  by  G.  T.  Darling  in  the  American  Jour- 
nal of  Public  Health  for  February,  1912.  From  this  the  following  is 
quoted : 

"  One  hundred  and  fifty  gallons  of  crude  carbolic  acid  are  heated  in 
an  iron  tank  having  a  steam  coil  with  steam  at  50  pounds  pressure. 
Two  hundred  pounds  of  finely  crushed  and  sifted  common  rosin  are 
dissolved  in  the  heated  acid,  and  then  30  pounds  of  caustic  soda  dissolved 
in  six  gallons  of  water  are  added.  There  is  a  mechanical  stirring  rod 
attached  to  the  tank.  The  product  is  ready  in  a  few  minutes,  yielding 
about  3|  barrels.  As  a  mosquito  larvicide  it  is  used  by  spraying  an 
aqueous  emulsion  (one  part  of  larvicide  to  five  of  water)  over  the  surface 
and  along  the  margin  of  pools  and  ponds  or  other  mosquito-breeding 
places  so  that  the  resulting  dilution  of  the  larvicide  has  a  thin,  milky 
opalescence  representing  approximately  a  dilution  of  1  to  5000."  Water 
thus  treated  is  poisonous  to  animals. 


MOSQUITO  CONTROL 


127 


Permanent  Corrections.  —  If  a  useless  pond  of  water  can  be  drained 
readily-  or  tilled,  and  this  is  very  often  the  case,  it  is  a  foolish  waste  of 


)^ 


■  .i,iijiJ*wgw^s;g^ 


•-*""^«»  -  ,^ 


^.* 


:  3^-.«— aaaaataia 


Tig  100  —  Upper  ht^uiv  shows  a  l.i-;  pond  a.l.iarcnr  td  the  lailn.ad  and  caused  by  ob- 
structing the  natural  drainage.  A  source  of  many  mosQuitoes  every  year  Oiling, 
while  serving  the  purpose,  requires  repeated  expenditure  of  time,  labor  and  money. 
The  lower  figure  shows  the  same  spot  after  it  had  been  permanently  corrected  by  the 
railroad  company. 

time,  energy  and  money  to  repeatedly  oil  it.  Marshy  land,  otherwise 
useless  for  agricultural  purposes,  can  in  many  instances  be  made  tillable 
and  at  the  same  time  free  from  mosquitoes  by  digging  ditches  of  neces- 
sary depth  together  with  proper  lateral  branches.  Thus  many  acres 
have  been  reclaimed,  made  productive  and  at  the  same  time  inhabit- 


128        MEDICAL  AND   VETERINARY   ENTOMOLOGY 

able.  The  dry  summers  prevailing  in  some  sections,  notably  California, 
favor  permanent  corrective  work,  because  pools  of  standing  water 
drained  off  at  the  termination  of  the  rains  in  spring  remain  dry  for  the 
rest  of  the  summer.  The  wisdom  of  permanent  corrective  measures  is 
recognized  by  all  larger  business  interests  as  witnessed  by  their  response 
to  requests  for  aid  in  mosquito  control  (Fig.  100). 

Irrigation.  —  It  is  quite  commonly  asserted  that  malaria  makes  its 
appearance  together  with  irrigation.     That  is  apparently  true,  but  it 


Fig.  101.  —  Breaks  in  the  irrigation  ditch  are  rewpoiisible  for  considerable  inundation,  pro- 
ducing favorable  breeding  places  for  mosquitoes,  especially  Anopheles.  The  rapidly 
running  water  in  the  ditch  is  unfavorable  for  mosquitoes. 

need  not  be  so  if  proper  attention  were  paid  to  the  best  methods  of 
irrigation.  Certainly  southern  California  is  necessarily  the  scene  of 
much  irrigation,  yet  malaria  is  quite  scarce,  therefore  irrigation  as  such 
cannot  be  a  factor.  The  matter  simply  resolves  itself  to  relative  abun- 
dance of  water ;  i.e.  where  this  is  abundant,  as  in  northern  California, 
it  is  used  unsparingly  and  without  regard  for  "  leaky  "  ditches  (Fig. 
101)  and  great  waste,  resulting  in  ideal  swamp  areas  for  the  propagation 
of  the  Anopheles  mosquito. 

With  proper  attention  to  irrigation  methods,  particularly  drainage 
(Fig.  102),  and  the  use  of  concrete,  tile  or  metal  waterways  to  prevent 
useless  lateral  seepage  there  need  be  absolutelv  no  malaria  associated 


MOSQUITO  CONTROL 


129 


therewith.  Water  should  not  be  permitted  to  stand  in  pools  for  long 
periods,  —  usuall}'  twenty-four  hours  is  sufficient.  Water  which  has 
been  standing  ten  days  or  over  is  dangerous,  because  it  only  requires 
ten  days  at  the  shortest  in  midsummer  for  the  commoner  species  of 
mosquitoes  to  develop  from  the  egg  to  the  adult.  W^ater  that  runs 
freely  in  the  ditches  is  not  favorable  to  the  propagation  of  these  insects. 


Fig.  102. 


Drainage  water  resulting  from  irrigation,  a  source  of  myriads  of  mosquitoes. 
The  small  ditch  in  the  background  will  remove  the  difficulty. 


The  poorly  kept  ditch  is  a  bad  investment  in  every  way,  an  eyesore  and 
a  menace  to  health. 

River  Towns  and  Malaria.  —  As  long  as  a  river  is  high  there  will  be 
little  or  no  opportunity  for  mosquitoes  to  breed  along  its  banks,  but 
later  in  the  summer,  during  June  and  July,  many  pools  are  left  behind 
by  the  receding  water  (Fig.  98).  The  stagnant  water  becomes  green 
with  algffi  and  soon  Anopheles  are  breeding  in  abundance.  The  same 
condition  also  commonly  prevails  along  smaller  streams.  Many  mos- 
quito wrigglers  may  often  be  found  developing  in  pools  covered 
with  green  scum,  and  along  the  edges  of  the  stream  or  creek  where  the 
current  is  very  sluggish.  In  both  cases  the  situation  is  controllable, 
as  has  been  demonstrated.  The  pools  along  the  banks  of  the  receding 
river  can  be  drained  off,  in  nearly  all  cases,  or  can  be  thoroughly  oiled. 
Thus  a  river  town  need  not  necessarily  be  a  malarial  town.  And  fur- 
thermore, the  banks  of  a  river  or  creek  can  be  kept  clean  at  a  compara- 
tively small  cost  and  this  need  only  be  done  for  a  distance  of  about  300 
yards  on  either  side  of  the  community ;  in  most  cases  a  hundred  yards 
less  will  serve  very  well  because  the  Anopheles  mosquitoes  are  not  strong 
fliers,  being  bred  as  a  rule  very  near  the  place  where  they  are  found. 

Salt  Marsh  Mosquitoes.  —  xVlthough  the  Anopheles  does  not  breed 
in  salt  or  brackish  water  to  any  great  extent,  some  of  the  most  formidable 
"  biters  "  do,  and,  moreover,  these  latter  may  be  carried  by  the  winds 


130 


MEDICAL  AND   VETERINARY   ENTOMOLOGY 


for  several  miles  from  their  breeding  grounds  and  make  life  miserable 
for  people  living  in  communities  unfortunate  enough  to  be  in  the  path 
of  the  invading  horde.  This  can  be  corrected,  however,  for  it  is  found 
that  not  all  portions  of  a  marsh  are  a  menace.  For  example,  the  writer 
examined  several  miles  of  marsh  in  a  given  locality  to  locate  the  source 
of  the  pest  and  discovered  that  the  breeding  ground  was  restricted  to  a 


Fig.   103.  —  Mosquito   control   work   on    a   large  scale.     Permanent  corrective  work,  — 
draining  a  large  pond  in  the  background.     Salt  marsh  work  in  California. 


comparatively  protected  area  comprising  only  a  few  acres.  For  control 
it  was  recommended  that  ditches  three  to  four  feet  deep  be  dug  from  the 
open  water  to  the  dry  land,  connecting  these  main  ditches  with  short 
laterals,  in  order  that  the  tide  waters  might  sweep  clear  in  and  also  to 
permit  the  extremely  voracious  little  killifishes  (Fundulus)  to  find  their 
way  unobstructed  into  every  nook  and  cranny  of  the  marsh. 

The  most  extensive  and  elaborate  salt  marsh  improvement  work  has 
been  done  in  New  Jersey  under  the  direction  of  Smith,^  the  permanent 
results  of  which  have  more  than  repaid  the  amount  appropriated  for 
the  purpose.  Land  which  was  previously  useless  became  available  for 
agricultural  purposes  and  for  summer  homes,  the  increase  in  real  estate 
valuation  being  an  important  factor  (Fig.  103). 

Summer  Resorts.  —  An  ideal  summer  resort  is  one  in  which  mos- 
quitoes do  not  take  a  prominent  part.     The  Anopheles  may  not  have 

^  Smith,  J.  B.,  1904.  Report  of  the  New  Jersey  State  Agricultural  Experi- 
ment Station  upon  the  Mosquitoes  occurring  within  the  state,  their  habits,  life 
history,  etc. 


MOSQUITO   CONTROL  131 

to  be  contended  with,  but  the  Culicine  species  are  found  more  or  less 
abundantly  everywhere  unless  measures  are  taken  to  control  them,  and 
some  of  our  summer  resorts  are  far  from  ideal  in  this  respect. 

Imagine  the  joy  and  comfort  of  a  mosquitoless  summer  resort  on  a 
fine  summer  evening  under  otherwise  favorable  circumstances,  when  it 
is  possible  to  sit  on  the  veranda  without  having  to  fight  mosquitoes  all 
the  time !  The  ease  with  which  these  pests  can  be  controlled  and  the 
advertisement  that  a  mosquito-free  resort  deservedly  secures  should  set 
managers  working  in  this  direction. 

Screening.  —  Far  too  little  attention  has  been  paid  to  the  proper 
screening  of  sleeping  apartments.  The  time  will  come  when  screens 
will  no  longer  be  needed  against  intruding  mosquitoes  and  flies,  — 
indeed  that  day  has  already  dawned  for  a  few  (a  very  few)  thoroughly 
enlightened  communities,  which  have  discovered  that  these  noxious 
creatures  can  be  readily  controlled. 

Against  mosquitoes  nothing  larger  than  the  best  one-millimeter 
mesh  (No.  18)  screen  should  be  used.  Mosquitoes  are  persistent  and 
will  work  their  way  through  a  large  mesh.  Furthermore,  in  malaria- 
ridden  districts  it  is  time  well  spent  to  hunt  down  and  destroy  all  mos- 
quitoes that  may  have  secured  entrance  despite  the  screens.  It  is  also 
wise  to  carefully  screen  in  all  malaria  cases  at  night  so  that  Anopheles 
mosquitoes  cannot  become  infected  through  the  blood  of  such  patients. 

Campers,  prospectors,  soldiers,  and  others  required  to  sleep  out  of  doors 
should  use  special  folding  frames  covered  with  mosquito  netting.  These 
are  light  and  can  be  folded  to  convenient  size  for  portage  when  not  in  use. 

Cisterns,  fire  buckets,  and  other  water  receptacles  need  to  be  kept 
properly  screened  or  securely  covered. 

Repellents.  —  Night  laborers,  watchmen,  pickets,  and  others  com- 
pelled to  be  on  duty  at  night  are,  of  course,  exposed  to  the  bites  of  mos- 
quitoes and  should  exercise  some  precaution  at  least  against  these 
pests.  Repellents  of  several  kinds  have  been  used  with  more  or  less  suc- 
cess. The  writer  has  found  oil  of  citronella  to  be  one  of  the  most  reliable 
deterrents  when  simply  rubbed  on  the  hands  and  face ;  a  dozen  drops  or 
thereabouts  being  placed  in  the  hollow  of  the  hand  and  thus  applied. 

To  this  oil  may  be  added  various  other  ingredients;  for  example, 
Howard  has  found  the  following  mixture  most  effective,  viz. :  1  ounce 
of  citronella,  1  ounce  spirits  of  camphor,  and  one  half  ounce  oil  of  cedar. 
Howard  found  this  very  satisfactory  against  Cidex  pijnens  by  applying 
a  few  drops  on  a  bath  towel  hung  on  the  head  of  the  bed.  He,  however, 
adds  that  it  is  not  effective  against  the  yellow  fever  mosquito,  which 
begins  biting  at  daybreak  when  the  oil  has  lost  most  of  its  strength. 

Other  deterrents  used  and  recommended  by  various  authors  are  :  a  mix- 
ture of  castor  oil,  alcohol,  and  oil  of  lavender,  equal  parts  ;  or  a  few  drops 
of  peppermint  or  pennyroyal,  oil  of  tar,  oil  of  cassia,  or  simply  pure  kerosene. 

Repellent  Plants.  —  Much  has  been  written  about  deterrent  trees 
and  plants,  but  few,  if  any,  have  stood  the  test  of  accurate  observation. 


132        MEDICAL  AND   VETERINARY   ENTOMOLOGY 

The  writer's  own  experience  together  with  that  of  other  observers,  does 
not  credit  the  castor-oil  plant  nor  the  Eucalyptus  tree  with  important 
deterrent  properties;  the  same  seems  to  hold  true  of  the  chinaberry 
tree  and  the  pennyroyal  plant. 

Fumigants.  —  Knowing  that  mosquitoes  often  hibernate  in  great 
swarms  in  basements  of  buildings,  cellars,  and  other  favorable  situations, 
it  becomes  necessary  to  destroy  these  in  order  to  prevent  them  from 
propagating  in  the  spring  of  the  year.  A  number  of  very  satisfactory 
fumigating  agents  may  be  mentioned,  such  as  pyrethrum  powder,  sul- 
phur dioxid  (see  p.  75),  fumes  of  cresyl,  pyrofume  (a  turpentine  by- 
product), etc.  J.  B.  Smith  recommends  Jimson  weed  fumes  very  highly. 
He  recommends  using  powdered  Jimson  weed  (Datura  stramonhnn) 
at  the  rate  of  eight  ounces  per  1000  cubic  feet  of  space,  mixing  it  with 
one-third  its  weight  of  saltpeter  to  facilitate  combustion.  The  mixture 
is  to  be  spread  on  a  tin  pan  or  stone  and  ignited  at  several  points.  The 
fumes  are  not  dangerous  to  human  life. 

Mosquito  Bites.  —  Mosquito  bites,  while  perhaps  never  serious  in 
themselves,  may  lead  to  blood  poisoning  through  scratching  with  the 
finger  nails  in  the  attempt  to  relieve  the  irritation,  often  intense.  To 
relieve  this  irritation  any  one  of  the  following  may  be  applied,  viz.: 
ammonia,  glycerine,  alcohol  or  iodin.  According  to  Howard  the  most 
satisfactory  remedy  known  to  him  is  the  application  of  moist  toilet  soap. 
He  also  mentions  touching  the  puncture  with  a  lump  of  indigo  as  afford- 
ing instant  relief,  or  touching  the  parts  with  naphthaline  moth  balls. 

Natural  Enemies.  —  One  often  hears  others  say  that  there  is  a  natural 
"  balance  "  in  nature  which  should  not  be  disturbed,  and  this  argument 
is  frequently  advanced  against  the  efforts  of  those  engaged  in  mosquito 
control.  It  may  be  balm  to  such  individuals  to  know  that  mosquitoes 
have  also  their  natural  enemies,  if  man  can  indeed  be  considered  an 
unnatural  enemy. 

Among  the  less  efiicient  enemies,  owing  to  small  numbers,  are  the 
dragon  flies  (Odonata),  commonly  called  "  mosquito  hawks,"  "  snake 
doctors,"  and  "devil's  darning  needles."  These  insects  may  be  seen  in 
the  evening  darting  hither  and  thither  capturing  mosquitoes  and  midges 
on  the  wing.  Where  bats  are  plentiful,  these  animals  are  highly  spoken 
of  as  effective  enemies  of  mosquitoes. 

More  effective  enemies  are  found  among  the  surface-feeding  fishes, 
which  are  practically  all  of  small  size.  Unfortunately,  where  mosquito 
larvse  are  found  there  are  also  abundant  other  aquatic  insects,  so  that 
the  stock  of  fish  must  be  correspondingly  large  in  order  to  hold  in  check 
the  insects  aimed  at.  In  such  places  where  it  is  undesirable  to  apply 
oil  and  the  water  is  not  too  shallow  throughout  its  entire  extent,  fishes 
may  play  an  important  role ;  indeed  the  same  thing  may  hold  true 
in  bodies  of  water  where  it  is  quite  possible  to  apply  oil.  It  can  readily 
be  seen  that  to  transplant  fish  into  anything  but  permanent  bodies  of 
water  would    be   very  poor  policy.      Ornamental    ponds,   reservoirs. 


MOSQUITO   CONTROL  133 

springs,  cisterns,  tanks,  and  the  like  are  among  the  instances  in  which 
surface-feeding  minnows  may  be  fomid  usefuh 

The  common  goldfish  {Carassius  auratus)  is  at  the  same  time  one  of 
the  most  ornamental  as  well  as  efficient  fishes  in  this  respect.  The 
following  quotation  from  Howard  ^  after  Underwood,  referring  to  an 
ornamental  aquatic  garden  near  Boston,  in  which  mosquitoes  were 
kept  in  check  by  goldfish  is  apropos :  "I  took  from  the  pond  a  small 
goldfish  about  three  inches  long  and  placed  it  in  an  aquarium  where  it 
could  if  it  would,  feed  upon  mosquito  larvae  and  still  be  under  careful 
observation.  ...  In  the  first  day,  owing  perhaps  to  being  rather  easily 
disturbed  in  its  new  quarters,  this  goldfish  ate  eleven  larvae  only  in  three 
hours,  but  the  next  day  twenty-three  were  devoured  in  one  hour ;  and 
as  the  fish  became  more  at  home  the  '  wigglers  '  disappeared  in  short 
order  whenever  they  were  dropped  into  the  water.  On  one  occasion 
twenty  were  eaten  in  one  minute,  and  forty-eight  within  five  minutes. 
This  experiment  was  frequently  repeated  and  to  see  if  this  partiality  for 
insect  food  was  characteristic  of  those  goldfish  only  which  were  indige- 
nous to  this  locality  experimented  with,  some  said  to  have  been  reared 
in  carp  ponds  near  Baltimore,  Maryland,  were  secured.  The  result 
was  the  same.  .  .  ."  Similar  results  have  been  attained  in  a  number 
of  places  both  on  the  Atlantic  and  Pacific  coasts. 

One  of  the  most  valuable  articles  touching  the  control  of  mosquitoes 
by  fish  is  that  of  Seal  ^  for  the  Scientific  American,  in  which  he  makes 
the  following  statements :  "  The  goldfish  is  somewhat  lethargic  in 
habit,  and  is  also  omnivorous,  but  there  is  no  doubt  that  it  will  devour 
any  mosquito  larvae  that  may  come  in  its  way  or  that  may  attract  its 
attention.  The  one  great  objection  is  that  they  grow  too  large,  and  the 
larger  will  eat  the  smaller  of  them."  The  same  observer  concludes  that 
"  a  combination  of  the  goldfish,  roach,  and  top  minnows  would  prob- 
ably prove  to  be  more  generally  effective  in  preventing  mosquito  breed- 
ing than  any  other."  The  top  minnows  mentioned  are  Gamhusia  affinis 
and  Heterandria  formosa.  In  those  bodies  of  water  kept  free  from  mos- 
quito larvae  in  California,  McGregor,  working  for  the  writer,  has  observed 
that  the  following  three  species  are  primarily  concerned,  viz. :  the  Sacra- 
mento chub,  Leuciocus  crassicandra,  the  Sacramento  pike,  Ptychocheilus 
grandis;  and  the  shiner,  Lavinia  exilicauda.  The  Barbadoes  "  mil- 
lions "  (Cyprinodon  dispar)  has  been  found  useful  as  a  mosquito  de- 
stroyer in  that  country  and  elsewhere.  In  salt  marshes  the  tiny  killi- 
fishes  (Fundulus)  should  be  given  every  opportunity  to  reach  all  parts 
of  the  marsh.  Where  found,  they  are,  as  a  rule,  very  abundant  and  are 
efficient  as  destroyers  of  mosquito  larvae. 

Organization.  —  In  order  to  conduct  an  effective  civic  anti-malaria 
mosquito  crusade,  there  must  be  some  responsible  organization  back  of 
it.     This  may  be  a  new  body  or  an  organization  already  in  existence.     It 

1  Howard,  L.  O.,  1910  {loc.  cit.). 

2  Seal,  WiUiam  P.,  1908.    Scien.  Amer.  Suppl.,  Vol.  65,  No.  1691,  pp.  351-352. 


134        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

is  absolutely  essential  that  a  committee  at  least  be  responsible  as  a 
medium  between  the  citizens  and  the  persons  doing  the  actual  control 
work. 

In  the  several  anti-mosquito  crusades  under  the  writer's  direction 
the  financial  responsibility  was  undertaken  in  one  case  by  a  new  organ- 
ization under  the  name  of  "  The  .  .  .  Anti-Mosquito  League,"  with  a 
president,  vice  president  and  secretary  treasurer ;  in  another  case  it 
was  a  committee  of  representative  citizens  with  a  chairman,  a  secretary 
and  a  treasurer ;  the  committee  was  known  as  "  The  .  .  .  Anti-Malaria- 
Mosquito  Committee  " ;  and  in  still  another  crusade  the  responsibility 
was  undertaken  by  the  "  Mosquito  Committee  "  of  the  Woman's  Club. 
In  no  case  could  it  be  said  that  the  mosquitoes  were  worse  than  in 
neighboring  towns  which  might  have  led  to  such  action,  but  the  initia- 
tive could  be  traced  to  the  progressive  spirit  of  one  or  more  citizens. 

The  financial  responsibility  having  been  undertaken  by  the  respec- 
tive organization,  and  a  previous  estimate  of  cost  having  been  provided 
by  some  one  familiar  with  such  work,  the  next  step  in  the  campaign  is 
to  secure  the  services  of  a  trained  field  agent  or  sanitary  inspector  who 
is  to  do  the  actual  control  work  assisted  by  day  laborers. 

The  Inspector  or  Field  Agent  must  be  an  individual  not  only  quali- 
fied technically  but  must  have  the  ability  and  patience  to  inform  those 
with  whom  he  comes  in  contact  as  to  the  reason  for  his  action  if  the  work 
is  to  be  of  lasting  benefit.  This  does  not  imply,  of  course,  that  words 
should  be  lost  on  persons  who  purposely  interfere  on  the  ground  of  igno- 
rance, —  he  must  therefore  also  be  firm.  Since  sanitary  inspectors  in 
many  communities  are  grossly  incompetent,  and  are  merely  so-called 
inspectors,  whose  duty  it  is  to  occasionally  peer  into  a  toilet  or  tack  up 
a  contagious  disease  placard,  the  office  does  not  imply  the  dignity  that 
it  ought,  therefore  the  term  field  agent,  was  preferably  employed  in  the 
writer's  work  in  California. 

With  a  responsible  field  agent  in  charge  whose  sole  duty  it  is  to 
protect  the  health  of  the  community  through  the  control  of  mosquitoes 
the  success  of  a  crusade  should  be  assured. 

The  Cost.  —  The  cost  of  an  effective  campaign  is  thought  by  some 
to  be  quite  forbidding,  but  experience  under  conditions  often  apparently 
hopeless  has  shown  that  everything  necessary  can  be  done  within  rea- 
sonable limits.  One  good  field  agent  can  handle  from  eight  to  ten 
square  miles  of  territory,  and  the  salary  of  this  individual  represents 
the  greatest  outlay,  unless  much  permanent  corrective  work  is  done,  a 
matter  which  would  increase  the  cost  in  the  beginning,  but  would  pay 
in  the  long  run.  The  actual  field  work  need  not  extend  over  much  more 
than  eight  or  nine  months,  from  March  to  November  inclusive  at  most. 
Capable  men  can  usually  be  secured  at  a  salary  ranging  from  $75 
to  $125  per  month,  new  men  beginning  with  the  first  mentioned  sum. 

Considering  the  benefits  derived  in  added  comfort  and  improved 
health,  double  the  cost  above  mentioned  would  be  reasonable.     It  should 


MOSQUITO   CONTROL 


135 


be  noted  that  in  every  crusade  of  this  kind  the  general  health  conditions 
are  improved. 

In  order  that  a  campaign  may  be  successful  and  that  the  work  may 
continue  unhampered,  it  is  essential  that  sufficient  funds  be  in  sight  to 
begin  with.  Raising  funds  is  a  matter  that  must  be  settled  by  each 
community  for  the  present  until  such  legislation  has  been  brought  about 
that  will  insure  county  or  state  aid.  Thus  far  the  task  of  raising  funds 
has  ordinarily  been  given  over  to  the  civic  organizations  which  have 
solved  the  problem  in  one  way  or  another  through  committees.  Sev- 
eral committees  have  raised  their  funds  by  popular  subscription ;  one 
other  progressive  town  has  had  several  tag  days  with  gratifying  results. 

Under  California  conditions,  for  example,  the  average  minimum  cost 
of  protection,  giving  to  each  field  agent  an  area  of  ten  square  miles 
to  cover,  which  is  possible  with  some  assistance,  is  about  $.75  per  day 
per  square  mile.  At  this  rate  the  cost  of  an  average  crusade  covering 
an  area  of  ten  square  miles  is  about  $1600  for  one  season,  covering  a 
period  of  eight  months.  Estimating  the  cost  of  quinine  and  doctors' 
bills  at  $20  per  family,  with  not  more  than  one  hundred  families  within 
the  ten  square  miles  area  (a  low  estimate)  plus  25  per  cent  reduction  in 
earning  capacity  per  family  with  an  average  income  of  $800,  gives  a 
total  loss  of  $20  X  100  (=  $2000)  +  $800  X  100  X  25  per  cent 
(=  $20,000)  =  $22,000.  Ordinarily  it  is  possible  to  reduce  the  total 
amount  of  malaria  by  at  least  50  per  cent  in  one  season.  At  this  rate 
there  is  a  saving  of  $22,000  X  50  per  cent  -  $1600  =  $9400  (nine 
thousand  four  hundred  dollars)  in  one  season  to  this  scattered  rural 
community.     Surely  this  is  a  good  investment. 

The  following  table  (Table  II)  is  intended  to  give  an  idea  of  items 
involved  in  the  monthly  expense  account. 


TABLE  II 

Tabular  Account  of  Monthly  Expenses  (for  Oroville)^  from  March  to 

July  Inclusive,  1911 


March  and  Apml 

May 

June 

July 

Oil       

Rig  hire 

Printing  and  stationery  . 

Postage 

Labor  2 

Sulphur 

Field  Agent 

$15.10 

9.50 

11.50 

1.60 

March  10.00 
1  April    125.00 

$2.50 
10.50 

.50 
125.00 

$16.90 
9.00 

2.00 
.50 

125.00 

$25.45 
9.00 

.50 
125.00 

$182.70 

$138.50 

$153.40 

$159.95 

1  The  greater  part  of  this  work  was  confined  to  an  area  of  about  four  square 
miles,  including  the  city  of  Oroville,  California,  and  only  about  one  fifth  of  the 
time  was  spent  in  inspecting  the  rural  surroundings. 

-  Practically  all  labor,  to  the  value  of  approximately  $120,  paid  by  city 
street  department  and  several  private  companies. 


136 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


The  above  estimate  of  $.75  a  day  per  square  mile  of  protection  does 
not  include  much  permanent  corrective  work,  and  would  continue  from 
year  to  year  without  lessening  greatly,  though  the  educational  factor 
will  play  an  important  part  after  two  or  three  years,  when  individuals 
in  a  community  will  do  considerable  work  of  their  own  accord. 

The  following  estimate  (Table  III),  based  on  a  thirty  square  mile 
area  and  including  all  necessary  permanent  corrective  work  of  ordinary 
nature,  shows  conclusively  that  a  larger  primary  investment  is  the 
cheapest  in  the  end  and  certainly  far  more  satisfactory. 

TABLE  III 

Estimated  Cost  of  Malaria  Control  Covering  a  Thirty  Square 
Mile  Tract  and  Including  all  Ordinary  Permanent  Corrections. 
Based   on  a   Taxation  Plan. 


Items 


Assessor 

Director 

Field  Agents 

Surveys     

Maps 

Stenographer      .... 
Equipment  (Teams,  etc.) 

Labor    

Materials 

Feed 

Supplies 

Office  (postage,  etc.)    .     . 

Oil 

Incidentals 

Ten  per  cent  contingencies 


First  Year 


Approximate    cost 
mile  per  day    . 


per   square 


$1000 

2500 

3200  (3) 

2500 

750 

900 

2000 

3000 

1500 

700 

100 

100 

350 

200 

' 18800 

^880 

Square  miles  30)20680 
Days  365)689 


$1.90 


Second 
Ye.vr 


$500 

2000 

2400  (2) 


200 

200 

250 

50 

100 

200 

100 

6000 

600 

30)6600 

365)220 


$.60 


Third 
Year 


$200 
400 

1500  (1] 


100 

120 

100 

100 

100 

2620 

262 

30)2882 

365J96 

$.27 


When  to  Begin  Work  and  when  to  Close.  —  The  best  results  are 
secured  in  a  new  district  by  eliminating  as  far  as  possible  the  last  brood 
of  mosquitoes  in  the  autumn,  i.e.  oil  or  drain  off  all  mosquito  breeding 
pools  in  October  and  go  over  the  territory  once  again  in  November. 
In  this  way  the  number  of  mosquitoes  which  hibernate  over  winter  is 
reduced  to  a  minimum.  The  spring  work  should  begin  in  March, 
depending  on  the  weather,  —  if  warm,  the  work  must  begin  earlier  in 
the  month,  if  cool,  then  later.  This  can  only  be  ascertained  by  inspect- 
ing likely  pools  in  order  to  determine  whether  mosquito  larvae  are  pres- 


MOSQUITO  CONTROL  137 

ent  and  what  size  they  have  attained.  Usually  the  last  larvse  are  found 
in  October  and  the  campaign  may  usually  close  safely  with  the  end  of 
this  month.  This  applies  to  the  Anopheles  mosquito  (the  malaria 
bearers)  and  does  not  apply  to  the  Culicine  varieties,  including  salt 
marsh  species. 

The  Educational  Factor.  —  Giving  the  answer  to  the  questions, 
"  Why?  "  and  "  How?  "  is  the  part  the  educator  must  play  in  the 
science  of  sanitation.  If  once  the  people  of  a  town  or  village  catch  the 
vision  of  better  things,  and  are  taught  how  to  realize  these  things,  the 
problem  is  largely  solved. 

To  help  answer  these  questions  at  least  one  lecture,  well  illustrated 
by  means  of  charts,  lantern  slides,  and  other  material,  should  be  given 
at  the  beginning  of  each  campaign.  This  we  generally  follow  up  with 
brief  newspaper  articles,  for  the  press  is  one  of  the  greatest  educational 
factors  in  America.  Show  window  displays,  in  which  the  properly  labeled 
living  insects  are  exhibited  as  they  pass  through  their  various  stages  of 
development.  Also  the  action  of  the  oil  can  be  thus  nicely  illustrated. 
The  interest  that  this  sort  of  display  arouses  is  immense  and  few  mer- 
chants hesitate  to  allow  at  least  a  part  of  their  windows  to  be  so  used. 

A  laboratory  may  or  may  not  be  established  in  which  the  more 
scientific  phases  of  the  subject  are  illustrated  by  means  of  the  microscope 
and  other  apparatus.  The  writer  has  found  such  laboratories  very 
valuable  since  it  gives  the  field  agent  an  added  impetus  and  adds  to  his 
efficiency  in  the  field.  Here  the  more  detailed  habits  of  the  individual 
insect  can  be  observed. 

One  of  the  most  important  factors  in  our  work  is  that  accomplished 
through  the  school  children.  The  school  children  are  visited  in  the 
classroom  and  the  story  of  the  mosquito  wriggler  is  told,  —  how  the 
mosquito  carries  disease  and  how  to  prevent  it.  Demonstrations  with 
the  living  wrigglers  can  easily  be  made.  Interesting  essays  are  then 
written  by  the  children  and  the  best  may  be  published  in  the  local  paper, 
all  of  which  stimulates  interest  and  gives  the  children  a  grasp  on  prac- 
tical subjects.  The  lessons  (Fig.  104)  learned  at  this  time  will  be  ap- 
plied at  once,  and  a  generation  of  citizens  is  reared  with  some  knowledge 
of  practical  hygiene. 

The  use  of  a  mosquito  pin  or  button  has  resulted  in  much  good.  On 
answering  some  simple  question,  or  after  putting  oil  on  a  pool  of  water, 
the  child  receives  such  a  pin  from  the  inspector  as  a  reward  of  merit. 

Legislation.  —  In  any  malaria  crusade  all  the  inhabitants  of  a  given 
district  are  equally  benefited  ;  it  is  therefore  unreasonable  that  the  en- 
tire cost  of  a  campaign  should  be  borne  by  a  few  individuals,  which  has 
been  the  case  in  several  localities  where  funds  were  contributed  through 
popular  subscription.  Because  of  the  equal  benefits  derived,  some  plan 
of  assessment  or  state  appropriation  seems  to  be  more  reasonable ;  how- 
ever, the  latter  (state  appropriation)  may  be  objectionable  unless  all 
parts  of  the  state  are  concerned.     It  should  be  borne  in  mind  after  all 


138 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


that  bad  advertising  for  one  part  of  the  state  means  injury  to  every 
other  part,  and  the  fact  that  malaria  is  present  in  any  state  is  bad 
advertising.  Be  it  also  known  that  no  community  can  hide  the  fact 
that  malaria  is  present  within  its  bounds,  however  strenuously  its  pres- 
ence is  denied.  To  carry  on  an  anti-malaria  campaign  and  then  to 
widely  advertise  the  fact  is  the  best  sort  of  advertising.  Note  the 
change  of  heart  suffered  by  real  estate  dealers  and  boosters  in  several 
of  the  more  progressive  towns  in  malaria-ridden  districts. 


Fig.  104.  —  School  children  taking  lessons  in  practical  hygiene.  The  little  boy  in  the 
foreground  is  preaching  the  gospel  of  good  health  to  hundreds  of  children  in  many 
parts  of  the  land  by  this  example. 


In  January,  1911,  an  act  known  as  the  Guill  Bill  was  introduced  in 
the  California  legislature,  and  was  passed  by  both  houses,  but  did  not 
receive  the  governor's  signature.  Had  this  bill  become  a  law,  it  would 
have  been  the  first  state  enactment  of  its  kind  in  the  United  States 
directed  specifically  towards  the  extermination  of  the  Anopheles  mos- 
quito by  local  communities  with  the  object  of  controlling  malaria. 

The  bill  provided  that  the  Board  of  Supervisors  in  any  county,  on  its 
own  motion  or  upon  receiving  a  petition  from  ten  or  more  taxpayers  in 
the  proposed  district,  should  pass  a  resolution  declaring  its  intention  to 
do  all  work  necessary  for  the  extermination  of  Anopheles  mosquitoes, 
describing  the  boundaries  of  the  district  to  be  benefited  and  assessed 
for  the  benefits.  The  petition  mentioned  was  required  to  give  the  bound- 
aries of  the  proposed  district,  to  show  that  a  survey  had  been  made 
of  the  district  under  the  direction  of  the  State  Board  of  Health,  and 


MOSQUITO  CONTROL  139 

that  such  survey  showed  that  there  were  one  or  more  breeding  places 
of  Anopheles  mosquitoes  within  the  proposed  district. 

The  resolution  of  intention  to  do  the  work  was  required  to  be  pub- 
lished, and  opportunity  was  given  to  any  one  who  objected  to  the  work 
to  appear  before  the  Board  and  state  his  reasons  for  objecting.  If 
they  were  not  valid,  the  Board  was  to  proceed  to  order  the  work  done, 
appointing  three  commissioners  to  assess  benefits  and  damages  and  have 
general  supervision  of  the  work.  These  commissioners  were  to  have 
made  a  thorough  sanitary  survey  of  the  district,  make  and  map  a 
careful  description  of  the  work  required,  and  report  the  same  to  the 
Board  of  Supervisors.  All  objections  to  this  report  or  any  portion 
of  it  were  then  to  be  filed  in  writing  with  the  county  clerk,  and  at  the 
next  regular  meeting  of  the  Board  these  objections  were  to  be  heard  and 
sustained  or  rejected  or  modified  according  to  the  judgment  of  the  Board. 

Certified  copies  of  the  report,  assessment  roll,  and  map  were  then  to 
be  filed  with  the  tax  collector,  the  taxes  were  then  to  be  payable,  and 
work  to  proceed  as  funds  became  available. 

The  state  of  New  Jersey  enacted  effective  legislation  against  salt 
marsh  mosquitoes  in  1906 ;  the  act  reads :  "  An  act  to  provide  for 
locating  and  abolishing  mosquito-breeding  salt  marsh  areas  within  the 
state,  assistance  in  dealing  with  certain  inland  breeding  places,  and 
appropriating  money  to  carry  its  provisions  into  effect  "  and  "  for  the 
purpose  of  carrying  into  eff'ect  the  provisions  of  this  act,  the  said  Direc- 
tor of  the  State  Agricultural  Experiment  Station  shall  have  power  to 
spend  such  amount  as  may  be  appropriated  by  the  legislature,  provided 
that  the  aggregate  sum  appropriated  for  the  purpose  of  this  act  shall 
not  exceed  three  hundred  and  fifty  thousand  dollars." 

The  first  sound  county  legislation  in  the  state  of  California  has  been 
enacted  by  the  county  of  Tehama  and  reads  as  follows  : 

"  Ordinance  No.  46 

"  An  ordinance  to  exterminate  the  mosquito  larva. 

"The  Board  of  Supervisors  of  the  County  of  Tehama,  State  of  Cahfornia, 
do  ordain  as  follows : 

"  Section  1.  No  person  or  persons,  firm  or  corporation  shall  discharge, 
pour,  empty  out,  or  otherwise  place  upon  the  surface  of  the  ground  in  any  lot, 
yard,  street,  road,  alley  or  premises  within  the  Hmits  of  the  County  of  Tehama, 
State  of  California  any  water  from  any  source  which  remains  in  a  stagnant 
condition  within  two  thousand  (2000)  feet  of  any  occupied  dwelling  house,  or 
maintain  water  in  stagnant  condition  in  any  barrel,  can,  tub  or  open  re- 
ceptacle of  any  character  whatsoever,  within  two  thousand  (2000)  feet  of  any 
occupied  dwelling  house.  The  presence  of  the  mosquito  larva  in  said  water  shall 
be  conclusive  evidence  that  said  water  is  stagnant,  and  upon  the  finding  of  said 
mosquito  larva  the  occupant,  or  if  the  premises  arc  unoccupied,  the  owner, 
shall  be  liable  to  arrest,  fine  and  imprisonment  as  hereinafter  provided,  and  if 
the  said  stagnant  water,  which  is  hereby  deemed  a  nuisance,  be  not  drained 
away  or  treated  in  a  manner  satisfactory  to  the  Health  Officer  of  Tehama 
County  or  his  authorized  representative,  and  within  a  reasonable  period  of 


140        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

time  as  determined  by  the  Health  Officer  or  his  authorized  representative,  the 
said  nuisance  shall  be  abated  by  the  Health  Officer.  The  cost  thereof  shall  be 
paid  from  the  General  Fund  of  the  Treasury  of  Tehama  County  upon  sworn 
warrant  of  the  Health  Officer,  and  the  cost  of  said  abatement  shall  be  a  lien 
upon  the  property  upon  which  the  said  nuisance  was  created  and  abated,  and 
shall  be  collected  by  law  as  taxes  are  collected. 

"  Section  2.  Wells,  cisterns,  cesspools  and  privy  vaults  shall  be  so  screened 
or  covered  as  to  prevent  access  to  the  contents  thereof  by  mosquitoes,  and 
such  screens  or  covering  shall  be  maintained  in  good  condition  and  to  the  satis- 
faction of  the  Health  Officer  of  Tehama  County. 

"Section  3.  All  violations  of  this  ordinance  shall  be  a  misdemeanor,  pun- 
ishable by  a  fine  of  not  less  than  five  (15.00)  dollars  nor  more  than  fifty 
($50.00)  dollars,  or  by  imprisonment  in  the  County  Jail  for  not  less  than  five 
(5)  days  or  more  than  fifty  (50)  days,  or  by  both  such  fine  and  imprisonment." 

Malaria  Reduction  as  the  Result  of  Anti-mosquito  Measures  is 

nicely  shown  by  the  following  table  (Table  IV)  after  Cassa :  ^ 

TABLE  IV 
Showing  Deaths  from  Malaria  in  Havana  from  1872  to  1911  Inclusive 

The  enormous  reduction  in  deaths  will  be  seen  to  begin  with  the  inauguration 
of  anti-mosquito  measures  in  1901. 


Years 

Total  Deaths 

Death  Rate 

Years 

Total  Deaths 

Death  Rate 

1871 

262 

1.33 

1892 

286 

1.33 

1872 

316 

1.60 

1893 

246 

1.12 

1873 

329 

1.61 

1894 

201 

0.90 

1S74 

288 

1.45 

1895 

206 

0.90 

1875 

284 

1.43 

1896 

450 

1.95 

•1876 

334 

1.68 

1897 

811 

3.48 

1877 

422 

2.12 

1898 

1907 

8.00 

1878 

453 

2.28 

'  1899 

909 

3.76 

1879 

343 

1.72 

1900 

325 

1.30 

1880 

384 

1.93 

1901 

151 

0.55 

1881 

251 

1.26 

1902 

77 

0.29 

1882 

223 

1.12 

1903 

51 

0.19 

1883 

183 

0.91 

1904 

44 

0.16 

1884 

196 

0.98 

1905 

32 

0.11 

1885 

101 

0.50 

1906 

26 

0.08 

1886 

135 

0.67 

1907 

23 

0.08 

,1887 

269 

1.34 

1908 

19 

0.06 

1888 

208 

0.99 

1909 

6 

0.01 

1889 

228 

1.11 

1910 

15 

0.05 

1890 

256 

1.23 

1911 

12 

0.03 

1891 

292 

1.37 

Figures  105  and  106  show^  graphically  the  results  of  anti-mosquito 
work  at  Ismailia  and  at  Panama. 

^  Cassa;  Jorge  Le  Roy  Y.,  1913.     Sanitary  Improvement  in  Cuba  as  demon- 
strated by  statistical  data.     Amer.  Journ.  of  Public  Health,  No.  3,  Vol.  III. 


MOSQUITO   CONTROL 


141 


Results  Obtained  in  Combating  Yellow  Fever  Mosquitoes.  —  The 
table  on  next  page,  taken  from  Doane/  shows  the  death  rate  in  Havana 


Fig.    105.  —  Curve  showing  reduction  of  malaria  at  Ismailia  (Suez  Canal)  with  the  appli-. 
cation  of  anti-mosquito  measures  in  1902. 

due  to  yellow  fever  from  the  years  1893  to  1902  inclusive ;  the  work  of  the 
Yellow  Fever  Commission  based  on  mosquito  control  having  been  put 


m 

.  _  #   .          -    --.-^  •-- .  1 

/>fa/ar/a  jya/zs/zcs  or 

»— [« 

/wy  -year    ^A-firf  revw/-*-^//*/? 

■    /    •*>       1  \ 

7    '"'     1  \ 

1  ij^i  y 

MV               > 

» 

AOO               [ 

^-^-i^-_*    =   .   \ 

:  M  1  1  1  1 

1  1  1  i 

■   \   \   \   \  \   \   \   \   \- 

i 

Fig.   106.  —  Curve  showing  reduction  of  malaria  at  Panama  (Panama  Canal  Zone)  with 
the  application  of  anti-mosquito  measures  in  1901. 

into  effect  in  1901  and  1902.     Surely  this  table  is  eloquent  in  its  praise 
of  this  splendid  work. 


1  Doane,    R.    W.,   1910.     Insects  and  Disease.     Henry  Holt  &  Co.,  New 
York.     pp.  xiv  +  227. 


142        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

TABLE   V 

Deaths  in  Havana  from  Yellow  Fever  during  Years  1893  to  1902 

Inclusive 


1893 

1894 

1896 

1896 

1897 

1898 

1899 

1900 

1901 

1902 

January  .     . 

15 

7 

15 

10 

69 

7 

1 

8 

7 

0 

February 

6 

4 

4 

7 

24 

1 

0 

9 

5 

0 

March     .     . 

4 

2 

2 

3 

30 

2 

1 

4 

1 

0 

April  .     .     . 

8 

4 

6 

14 

71 

1 

2 

0 

0 

0 

May    .     .     . 

23 

16 

10 

27 

88 

4 

0 

2 

0 

0 

June    .     .     . 

69 

31 

16 

46 

174 

3 

1 

8 

0 

0 

July    .     .     . 

118 

77 

88 

116 

168 

16 

2 

30 

1 

0 

August     .     . 

100 

73 

120 

262 

102 

16 

13 

49 

2 

0 

September    . 

68 

76 

135 

166 

56 

34 

18 

52 

2 

0 

October  .     . 

46 

40 

102 

240 

42 

26 

25 

74 

0 

0 

November    . 

28 

23 

35 

244 

26 

13 

18 

54 

0 

0 

December     . 

11 

29 

20 

147 

8 

13 

22 

20 

0 

0 

CHAPTER   XII 


BUFFALO  GNATS  AND  HORSEFLIES 


A.     Buffalo  Gnats 


Order  Diptera,  Suborder  Nematocera,  Family  Simuliidoe 

Characteristics.  —  To  the  family  Simuliidfe  belong  the  tiny  blood- 
sucking flies  commonly  callefl  buffalo  gnats,  black  flies,  sand  flies  and 
turkey  gnats.  They  are  small  dipterous  insects  ranging  from  1  to  4  mm. 
in  length,  with  a  curiously  humped  thorax  (Fig.  107)  and  blade-like  pierc- 
ing mouth  parts.  The  antennae  are  short  cylindrical  structures  consist- 
ing of  eleven  segments.  The 
wings  are  relatively  broad  and 
iridescent,  and  the  venation  is 
characterized  by  the  strong  de- 
velopment of  the  costal  veins, 
the  remaining  ones  being  very 
weakly  developed  or  absent. 
The  Simuliidse  are  world-wide 
in  their  distribution. 

Larvae.  —  The  brown  to 
whitish  larvse  are  cylindrical, 
twelve-segmented,  slightly 

thinner  in  the  mid  region,  and 
when  fully  grown  are  from  10 
to  15  mm.  in  length  (Fig.  108a). 
The  posterior  end  of  the  body 
is  provided  with  a  toothed  disk- 
like sucker,  composed  of  two 
modified  parapodia.  The  an- 
terior  proleg   is  also    modified 

into  a    prehensile    toothed    disk.   Fig.  107.  -  a  buffalo  gnat,  6WZmm  sp.    X18. 

By  means  of  this  organ,  the  larva  moves  from  place  to  place  with  a 
looping  motion.  Through  the  agency  of  a  secretion  from  the  salivary 
glands,  the  larvae  are  able  to  spin  a  silken  thread  to  which  they 
attach  themselves,  hanging  from  the  end  of  the  thread  or  moving 
along  its  length,  the  thread  being  attached  to  rocks  or  other  debris. 
Although  the  larvae  are  provided  with  a  well-developed  tracheal 

143 


144        MEDICAL  AND   VETERINARY  ENTOMOLOGY 


system,  there  are  no  open  spiracles,  and  respiration  is  carried  on  by 
means  of  ^ills,  recognized  as  branched  retractile  structures  located 
dorsally  on  the  last  abdominal  segment.  The  fan-shaped  filamentous 
structures  located  on  the  head  are  for  the  purpose  of  creating  a  current 
by  means  of  which  food  is  drawn  to  the  mouth. 

Pupae.  —  The  pupse  are  quiescent  and  are  loosely  encased  in  silken 
cocoons  or  pockets.  They  are  provided  anteriorly  with  a  number  of 
long  tracheal  filaments  (Fig.  1086),  which  are  also  of  importance  in 
classification. 

Breeding  Habits  and  Life  History.  —  The  adult  bufYalo  gnats  often 
occur  in  great  swarms  during  the  late  spring  and  early  summer  in  the 

neighborhood  of  marshes  and  forest 
streams.  Occasionally  swarms  of  these 
insects  are  seen  far  removed  from 
moisture,  but  the  reason  for  this  is 
usually  traceable  to  prevailing  winds. 
At  this  time  of  the  year  the  tiny  white 
or  whitish  eggs  are  deposited  in  great 
numbers  on  the  exposed,  preferably 
wet,  surfaces  of  rocks,  grass,  moss, 
brush  and  other  debris  in  shallow 
streams  of  rather  swiftly  running  water 
by  preference.  Comstock  says  he  has 
often  watched  the  gnats  hovering  over 
the  brink  of  a  fall  where  there  was  a 
thin  sheet  of  swiftly  flowing  water,  and 
has  seen  them  dart  into  the  water  and 
out  again.  At  such  times  he  has  al- 
^  I  ways  found    the  surface  of    the   rock 

^      ,^„       ,  ,  ,  ,  ,,,  more  or  less  thicklv  coated  with  eggs, 

Fig.  108.  —  (a)    Larva   and    (o)    pupa  ,  ,  i       i  ^  ^i"    j^  •     e      j  ^ 

of  Simuiium ;  latter  removed  from    and  has  no  doubt  that  an  egg  IS  lastcned 
cone-shaped  cocoon  (Redrawn  after    ^^  ^he  rock  each  time  a  fly  darts  into 

Lugger  from  Washburn.)  '' 

the  water. 

The  time  required  for  hatching  is  from  ten  to  thirty  days,  depending 
on  temperature.  The  newly  emerged  larvae  attach  themselves  to  sub- 
merged objects,  such  as  stones,  logs,  etc.,  by  means  of  silken  threads. 
Movement  from  place  to  place  is  gained  by  shifting  their  anchorage.  In 
some  favorable  location,  such  as  the  riffles  on  the  downstream  side  of  an 
old  log  partially  damming  a  little  stream,  there  may  be  thousands  of 
these  tiny  spindled  larvae.  The  larvae  as  well  as  the  pupae  being 
provided  with  gill  filaments  remain  submerged.  Growth  is  slow,  the 
larval  period  covering  the  time  from  early  summer  to  the  following 
early  spring,  when  full  larval  growth  is  reached.  The  larval  period  of 
some  species  is  said  to  require  but  four  to  five  weeks.  The  food  of 
the  larvae  consists  of  small  Crustacea,  protozoa  and  algae. 

The  pupal  period  is  quite  short  in  some  species,  requiring  not  over 


BUFFALO  GNATS  AND   HORSEFLIES  145 

five  or  six  days,  while  still  others  evidently  require  nearly  a  month.  It 
is  also  true  that  temperature  influences  this  stage,  i.e.  cooler  weather 
retards  the  emergence  of  adults. 

The  Bite.  —  There  is  perhaps  no  other  insect  of  equal  size  that  can 
inflict  so  painful  a  bite  as  can  the  buft'alo  gnat.  The  mouth  parts  are  of 
the  Dipteron  type,  consisting  of  six  blade-like  lancets. 

Human  beings  as  well  as  domesticated  animals  are  viciously  attacked. 
The  eyes,  ears,  nostrils,  wrists  and  all  exposed  parts  of  the  body  are 
subject  to  attack.  The  extreme  pain  and  the  resultant  local  swelling, 
and  occasionally  complications,  indicate  the  introduction  of  an  active 
venom. 

Losses  due  to  the  bite  of  this  fly  are  estimated  variously  by  stock- 
men. Washburn  ^  states  that  "  in  1884,  in  Franklin's  Parish,  Louisiana, 
they  killed  300  head  of  stock  in  a  week.  In  1874  the  state  of  Tennessee 
alone  lost  as  much  as  $500,000  worth  of  stock  from  the  attack  of  these 
flies." 

Relation  to  Disease.  —  Owing  to  the  intermittent  blood-sucking 
habits  of  the  buft'alo  gnats,  it  has  long  been  suspected  that  these  in- 
sects might  play  a  part  in  the  transmission  of  disease,  but  as  a  matter 
of  fact,  little  experimental  evidence  is  at  hand  to  verify  this  suspicion. 
Since  anthrax  is  comparatively  easily  transmitted  from  animal  to  ani- 
mal, inasmuch  as  Bacillus  anthracis  is  both  exceedingly  virulent  and  long- 
lived,  it  may  be  supposed  that  this  disease  could  be  transmitted,  if  any, 
but  even  here  experimental  evidence  is  wanting. 

Since  the  rather  startling  statement  of  Dr.  Louis  W.  Sambon  ^  in 
1910,  referring  the  transmission  of  pellagra  to  a  buffalo  gnat,  the  study 
of  Simuliidse  with  regard  to  disease  transmission  has  taken  new  impetus. 

Pellagra.  —  This  disease,  also  known  as  Alpine  scurvy,  sun  disease 
and  Asturian  leprosy,  has  a  very  wide  geographical  distribution  in  semi- 
tropical  countries,  especially  southern  Europe.  In  the  southern  United 
States  the  disease  has  been  increasing  an  hundred  fold  during  the  past 
two  years  or  more. 

The  disease  is  manifested  by  annually  recurring  attacks  of  nervous 
and  cutaneous  symptoms.  The  symptoms  reappear  each  year  in  the 
spring,  gradually  disappearing  during  the  winter.  The  nervous  symp- 
toms are  mainly  in  the  form  of  melancholia,  while  the  cutaneous  symp- 
toms are  in  the  form  of  eruptions  influenced  by  sunlight. 

Both  sexes  are  alike  susceptible  as  well  as  all  ages,  except  rarely 
infants.  That  the  disease  is  most  widespread  among  field  laborers  and 
country  folk  living  near  streams  of  water,  and  that  the  symptoms  recur 
with  the  spring  months  has  led  to  an  investigation  of  the  insect  carrier 
theory.     Heretofore  the  maize  theory  of  spread  was  most  generally 

1  Washburn,  F.  L.,  1905.     Diptera  of  Minnesota.     University  of  Minne- 
sota Agr.  Exp.  Sta.  Bull.  No.  93. 

2  Sambon,  L.  W.,  1910.     Progress  Report  Investigation  of  Pellagra.     Journ. 
of  Tropical  Medicine  and  Hygiene,  Vol.  XIII,  No.  19. 


146        MEDICAL  AND  VETERINARY  ENTOMOLOGY 

accepted,  i.e.  the  theory  that  the  disease  was  contracted  by  eating 
infected  corn  (maize). 

Dr.  Louis  W.  Sambon  {loc.  cit.)  of  the  London  School  of  Tropical 
Medicine  studied  the  pellagra  situation  in  Italy  and  in  1910  published  a 
note  on  his  investigations,  viz. :   "So  far  I  have  been  able  to  establish  : 

"  (1)  That  pellagra  is  not  due  to  the  eating  of  maize,  either  sound  or 
deteriorated,  as  hitherto  almost  universally  believed. 

"  (2)  That  it  has  a  striking,  peculiar  and  well  defined  topographical 
distribution. 

"  (3)  That  its  endemic  foci  or  'stations'  have  remained  exactly  the 
same  in  many  places  for  at  least  a  century. 

"  (4)  That  its  stations  are  closely  associated  with  streams  of  running 
water. 

"  (5)  That  a  minute  blood-sucking  fly  of  the  genus  Simulium  is  in 
all  probability  the  agent  by  which  pellagra  is  conveyed." 

Professor  H.  Garmen  of  the  Kentucky  Agricultural  Experiment 
Station  has  carried  on  recent  extensive  studies  with  regard  to  pellagra, 
and  his  findings  are  reported  in  Bulletin  159  (1912)  from  w^hich  the  fol- 
lowing extracts  are  taken,  viz. : 

"Looking  at  the  matter  from  the  point  of  view  of  the  entomologist  and 
naturalist  it  seemed  to  me  very  evident  when  I  had  examined  only  a  few  cases 
of  pellagra  that  some  agent  in  the  air  had  to  do  with  its  spread,  and  it  may  be 
of  interest  to  recall  the  facts  that  most  appealed  to  me.  In  the  first  place  the 
eruption  on  the  hands  began  apparently  about  the  bases  of  the  fingers  and  ex- 
tended thence  upward  to  the  elbows,  where  it  stopped  abruptlj'.  On  the  legs 
it  seemed  to  begin  at  the  feet,  affecting  the  upper  surface  and  extending  to  the 
knees,  where  it  terminated  in  a  well-marked  hne.  On  the  head  and  neck  it 
affected  in  all  cases  examined  only  the  skin  constantly  exposed,  and  terminated 
at  the  hair  and  at  the  collar.  Yet  in  some  instances  there  is  an  extension  of  the 
affected  skin  down  upon  the  chest,  coinciding  somewhat  closely  with  the  open- 
ing in  the  shirt  front.  One  such  case,  which  I  did  not  have  a  chance  to  see,  was 
reported  to  me  as  residing  at  Old  Straight  Creek,  above  Pineville.  All  of  these 
conditions  seemed  consistent  with  Dr.  Sambon's  theorj^  that  an  insect  carries 
the  virus  of  the  disease  from  ill  to  well,  attacking  the  exposed  skin  and  injecting 
into  it  something,  bacteria  or  protozoa,  which  gives  rise  to  the  disease. 

"Furthermore  the  disease  is  contracted  and  afterward  becomes  active  in  early 
spring  just  the  time  when  our  gnats  of  the  genus  Simulium  come  from  the  water 
in  greatest  numbers  as  adults. 

"Again  it  often  affects  children,  who  constantly  go  barefooted  and  bare- 
legged in  this  region  and  are  disposed  to  play  and  wade  in  the  streams.  Women, 
too,  were  affected  more  than  men,  about  the  anus  and  neck  generall.v,  but  also 
in  some  cases  on  the  feet  and  calves.  Men  go  less  frequently  with  limbs  bare, 
and  are  much  less  often  attacked.  The  skin  trouble  appears  upon  the  trunk 
rather  rarely,  though  cases  are  on  record  of  parts  generally  kept  covered  by 
clothing  becoming  affected. 

"With  these  facts  in  mind,  it  was  with  very  great  interest  that  I  examined  a 
case  at  Moss'  Camp  above  Pineville  which  seemed  to  oppose  the  idea  of  insect 
agency  in  the  disease.  The  case  was  that  of  a  middle-aged  woman  whose  arms 
showed  in  a  marked  manner  the  symmetrical  development  of  the  skin  lesions, 
so  often  mentioned  by  writers  on  the  ailment.  It  was  interesting  further  because 
it  was  then  (Sept.  1)  in  an  active  condition,  whereas  all  the  other  cases  examined 


BUFFALO   GNATS  AND   HORSEFLIES  147 

showed  the  usual  summer  cessation  of  the  disease  and  an  improvement  in  general 
health.  Tlie  affected  regions  on  the  two  arms  were  surrounded  by  a  deep  red 
border,  as  if  something  had  got  access  to  the  blood  in  the  center  of  the  area  and 
was  spreading  outward  into  the  health}^  skin,  much  as  one  sees  in  plants  a  fungus 
pushing  outward  from  a  point  of  inoculation  by  a  growth  of  its  mj'celium.  The 
area  on  the  two  anns  and  forearms  seemed  to  be  of  about  equal  extent.  This 
affected  region  was  sucli  as  might  at  some  time  have  been  exposed  to  the  air 
when  the  patient  was  busy  about  her  domestic  affairs.  A  n^.ore  interesting  and 
puzzling  feature  of  this  case  was  the  presence  of  two  isolated  round  spots  of 
diseased  skin,  one  on  the  iioint  of  each  shoulder.  If  there  had  been  one,  I  should 
have  thought  a  hole  in  a  gown  might  at  some  time  have  exposed  the  part  to 
infection,  but  the  chances  seem  against  the  presence  of  tw'O  such  holes  exactly 
alike,  one  on  each  shoulder.  I  am  giving  this  fact  as  an  illustration  of  what 
some  physicians  claim  to  be  an  invariable  feature  of  the  ailment,  no  matter 
where  the  skin  trouble  appears,  namely,  a  symmetry  in  the  skin  affection,  which 
they  regard  as  evidence  that  the  seat  of  the  disease  is  within  and  the  skin  lesions 
only  incidental  and  dependent.  The  case  appears  to  support  this  view,  yet  it 
may  prove  when  we  know  more  of  the  conditions  attending  the  contraction  of 
the  disease  that  such  cases  are  still  explainable  on  the  theory  of  insect  agency." 
Pellagra  has  been  carefully  studied  by  the  United  States  Public  Health 
Service,  and  in  the  Public  Health  Reports  of  October  23,  1914,  Goldberger 
states  that  Pellagra  is  neither  infectious  nor  contagious,  that  it  is  essentially 
of  dietary  origin,  dependent  on  some  yet  undetermined  fault  in  diet,  and  that 
the  disease  does  not  develop  in  those  who  consume  a  mixed,  well-balanced  and 
varied  diet. 

Gnat  Control.  —  Knowing  the  breeding  habits  of  the  buffalo  gnat,  it 
will  be  appreciated  that  its  control  is  a  difficult  task.  The  writer  has 
repeatedly  recommended  that  streams  in  which  these  insects  are  breeding 
should  be  kept  as  free  from  debris  as  possible,  including  dipping  branches 
of  overhanging  trees  and  submerged  roots.  It  is  possible  to  do  this  in 
the  immediate  vicinity  of  communities,  but  prevailing  winds  may  after 
all  bring  sw-arms  of  gnats  from  a  distance.  At  all  events  the  removal  of 
debris  from  streams  lessens  the  opportunity  for  them  to  deposit  their 
eggs.  Old  logs  lying  crosswise  of  a  stream  are  a  particular  menace 
because  shallow  waterfalls  are  thus  usually  produced,  hence  affording 
ideal  breeding  places  for  the  gnats. 

To  prevent  annoyance  to  beasts  of  burden  some  form  of  spray  or 
ointment  may  be  applied.  While  many  repellents  are  on  the 
market,  few  are  of  any  benefit  and  practically  none  affords  abso- 
lute relief.  Any  mixture  containing  fish  oil  is  of  some  benefit,  but  must 
be  applied  daily.  (See  also  under  Hornfly.)  Smudges  act  as  good 
repellents,  especially  burning  pyrethrum  pow'der  or  buhach.  Oil  of 
citronella  applied  to  the  skin  and  face  effectually  keeps  the  insects 
away  as  long  as  the  parts  remain  moist  with  the  oil. 

Systematic.  —  The  family  Simulidse  comprises  about  seventy-five 
described  species  (Williston),  all  in  the  same  genus,  i.e.  Simulium. 
Two  other  genera  are  recognized  by  Mallock,  namely,  Prosimulium 
and  Parasimuhum.  The  best-known  and  most  widely  distributed 
species  in  America  is  Simulium  yecuarum  Eiley,  the  buffalo  gnat. 
Riley's  description  is  here  given  as  abbreviated  by  Garmen : 


148        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

"Male.  Eyes  meeting  and  with  two  sets  of  facets.  Mouth  parts  soft. 
Head  black.  Antenna'  black,  with  some  red.  Maxillary  palpi  black.  Thorax 
black  above.  Abdomen  black,  with  grayish  white  posterior  margins  to  seg- 
ments. 

"Female.  'Eyes  not  meeting.  Head  gray  slate,  with  short  yellow  hairs. 
Eyes  black,  with  coppery  or  brassy  reflections.  Antennae  black  with  whitish 
pubescence.  Thorax  grayish  slate  and  generally  distinctly  marked  with  two 
mediodorsal  and  two  subdorsal  longitudinal  black  bands.  Under  side  of 
thorax,  grayish  slate.  Abdomen  wdth  a  broad  gray  longitudinal  band  from 
near  the  base  of  the  second  segment,  where  it  is  broadest. 

Simulium  vemistum  Say  is  the  black  fly,  a  widely  distributed  species 
extending  from  Canada  to  Texas  and  from  Florida  westward.  Say's 
description  is  as  follows : 

"Black:  thorax,  two  perlaceous  spots  before  and  a  larger  one  behind; 
poisers  black  ;   capitulum  bright  yellow,  dilated. 

"Body  black;   wings  whitish,  with  yellow  and  iridescent  reflections. 

"Male,  eyes  very  large,  separated  only  by  a  single  line,  dull  reddish  yellow, 
inferior  half  black ;  ^  thorax  velvet  black,  a  bright  oblique,  perlaceous,  dilated 
line  each  side  before,  and  a  large  perlaceous  spot  or  band  behind  ;  sides  beneath 
varied  with  perlaceous ;  feet,  tibia  above,  and  first  joint  of  the  four  posterior 
tarsi  white ;  abdon^en  witli  an  oblique  perlaceous  line  at  base,  and  two  approxi- 
mate, lateral,  perlaceous  ones  near  the  tip. 

"Female,  eyes  moderate,  thorax  plumbous-black,  unmaculate,  scutellum 
black,  abdomen  whitish  beneath." 

Simulium  meridionale  Riley  is  the  turkey  gnat,  which  also  enjoys 
wide  distribution  coinciding  with  the  buffalo  gnat.  This  species  at- 
tacks chickens  and  turkeys,  biting  the  combs  and  wattles,  and  is  said 
to  produce  symptoms  similar  to  cholera. 

Riley's  description  is  given  by  Garmen  as  follows : 

"The  male  is  from  1.5  to  2  mm.  in  length,  the  eyes  meeting  above,  where  the 
facets  are  coarser  and  of  a  brilliant  coppery  luster,  those  on  the  ventral  side 
smaller  and  black.  Thorax  dense  black  with  bluish  luster,  ventral  side  grayish. 
Legs  reddish  with  black  tarsi.  Abdomen  aliove  black,  posterior  margin  of 
segments  edged  with  gray.  Ventral  sides  of  segments  two  and  three  light 
reddish  gray,  the  rest  blackish  with  gray  posterior  margins." 

The  female  is  described  by  the  same  writer  as  from  "2.5  to  3  mm.  long ;  the 
head  slate-blue,  with  silvery  pubescence;  the  thorax,  with  three  longitudinal 
lines,  the  median  narrow  and  widening  at  the  apex,  the  outer  curving  in  at  the 
base  and  out  at  the  apex ;  beneath  slate-blue  ;  abdomen  with  last  five  segments 
dark  blue  above ;  segments  2,  3  and  4  each  with  a  black  cross  bar  :  segments  5, 
6  and  7,  with  two  submedian  stripes,  disappearing  on  7  ;  bluish  white  everywhere 
beneath;  legs  brownish  black." 

Simulium  occidentale  Townsend  is  perhaps  only  a  variety  of  the 
turkey  gnat  and  is  found  in  New  Mexico.  It  is  described  by  Town- 
send  as  follows : 

"This  species  is  smaller  than  either  *S.  pecuarum  or  S.  meridionale.  S.  occi- 
dentale differs  from  S.  pecuarum  very  markedly  in  the  thoracic  and  abdominal 
markings.     These  markings  are  very  much  like  those  of  S.  meridionale;  but  the 


BUFFALO   GNATS  AND   HORSEFLIES  149 

median  thoracic  line  is  always  very  faint,  the  abdomen  is  light  fulvous,  the 
lateral  lines  of  segments  5,  6  and  7  are  curved,  and  the  abdominal  markings  are 
of  a  different  color,  besides  other  minor  differences." 

Simulium  colwnhaczoue  Schoenbauer  is  the  Columbacz  midge  of 
Europe,  especially  abundant  in  the  Valley  of  the  Danube. 


B.   Horseflies 
Order  Diptera,  Suborder  Brachycera,  Family  Tabanidcs 

Introduction.  —  To  the  family  Tabanidse  belong  the  biting  flies 
commonly  called  horseflies,  gadflies  and  deer  flies.  All  the  genera  be- 
longing to  this  family  consist  of  large  flies  (10-25  mm.),  the  body  is  heavy 
and  the  head  possesses  very  large  eyes.  In  the  female  the  eyes  are  widely 
separate  (dichoptic),  while  in  the  males  the  eyes  are  contiguous  (holop- 
tic).  The  flight  is  very  swift  and  direct.  The  antennse  (Fig.  28)  are 
short  (Brachycera)  and  porrect,  consisting  of  three  joints,  the  third  joint 
being  annulated ;  the  arista  is  absent.  The  wing  venation  (Fig.  17) 
is  simple  and  characteristic. 

Larvae.  —  The  larvse  (Fig.  1096)  are  spindle-shaped,  tapering  at 
both  ends ;  are  eleven-segmented,  each  segment  being  clear  cut  and 
provided  with  a  circlet  of  tiny  spines  which  aid  in  locomotion.  The 
terminal  segment  bears  a  pair  of  stigmal  openings  and  is  somewhat 
prolonged  to  form  a  breathing  tube. 

Pupae.  —  The  pupte  (Fig.  1096-;  are  provided  with  a  conspicuous 
circlet  of  spines  at  the  apical  end  of  each  abdominal  segment. 

Breeding  Habits  and  Life  History. —  The  Tabanidse  are  aquatic  or 
semi-aquatic  in  breeding  habits.  The  eggs  to  the  number  of  two  to  three 
hundred  are  deposited  in  irregular  masses  (Figs.  109a-110)  on  marsh  or 
swamp  vegetation,  for  example  the  leaves  of  Sagittaria,  or  on  the  leaves 
and  twigs  of  trees  (e.g.  willows)  overhanging  ponds  or  sluggish  streams. 
In  the  Sierra  Nevada  mountains  horseflies  occur  in  great  numbers  at 
elevations  of  8000  to  9000  feet,  where  they  breed  in  the  soggy  ground 
produced  by  springs  and  water  from  the  melting  snow.  Deer  and  other 
wild  animals  suft'er  terrible  torment  in  the  summer  time  in  these  locali- 
ties from  the  bites  of  horseflies. 

The  eggs,  covered  with  a  protective  secretion,  are  deposited  in 
early  and  late  summer.  The  larvae  hatch  in  from  five  to  seven  days, 
depending  on  the  species,  the  larger  forms  requiring  somewhat  more 
time  than  the  smaller  ones.  The  larvse  on  hatching  fall  to  the  surface 
of  the  water,  penetrate  the  surface  film  and  then  drop  to  the  bottom,  or 
if  there  is  no  water,  the  larvse  burrow  into  soft  mud.  Moisture  is  cer- 
tainly necessary  for  their  development.  Insect  larvfe,  crustaceans  and 
other  soft-bodied  animals  provide  food  for  these  voracious,  carnivorous 
creatures  ;  cannibalism  is  also  practiced.    The  larvae  grow  rapidly  during 


150        MEDICAL  AND   VETERINARY  ENTOMOLOGY 


BUFFALO   GNATS  AND   HORSEFLIES 


151 


the  rest  of  the  summer  and  autumn,  and  very  slowly,  if  at  all,  during 
the  winter.  They  attain  full  growth  in  early  spring,  crawling  out  of  the 
softer  wet  mud  and  into  drier  earth,  where  they  pui)ate.  The  pupal 
period  requires  from  two  to  three  weeks.  The  emerging  flies  take  refuge 
among  the  foliage  of  near-by  trees  and  the  females  soon  begin  attacking 
warm  blooded  animals.  The  males  do  not  suck  blood,  but  feed  on  nec- 
tar and  other  plant  juices.  Unless  swept  up  with  an 
insect  net  in  grass  and  other  vegetation  the  males 
are  seldom  seen. 

Bites.  — •  The  horseflies  have  broad  blade-like 
mouth  parts  (Fig.  28)  by  means  of  which  a  deep 
wound  is  cut,  causing  a  considerable  flow  of  blood. 
The  bite  is  painful  and  owing  to  the  intermittent 
habits  of  the  flies  there  is  great  danger  from  infection. 

In  describing  an  outbreak  of  gadflies  in  Ken- 
tucky, Garmen  has  the  following  to  say :  ^  "  Beef 
cattle  had  lost  an  average  of  100  pounds  as  a  result 
of  the  constant  annoyance  from  them.  .  .  .  On 
cattle  I  counted  from  ten  to  nineteen.  On  mules 
and  horses  in  harness  they  were  a  constant  annoy- 
ance and  even  hogs  were  not  exempt.  Seven  of  the 
flies  were  counted  on  the  exposed  side  of  one  of  these 
animals  lying  in  a  puddle. 

"  The  persecuted  stock  appeared  to  have  given 
up  fighting  their  enemies  and  allowed  them  to  have 
their  way.  The  switch  of  a  cow's  tail  w^as  observed 
to  pass  over  the  backs  of  clinging  flies  without 
causing  them  to  move.  .  .  .  During  the  middle  of 
the  day  animals  suffered  so  much  that  they  re- 
frained from  grazing  at  all,  either  standing  close  to- 
gether about  the  barn  or  else  lurking  singly  in  thick- 
ets or  standing  in  pools  formed  by  small  streams." 

Relation  to  Anthrax.  —  The  horseflies  are  de- 
cidedly intermittent  in  their  biting  habits,  and  inflict  a  definite  lancet- 
like prick  from  which  blood  exudes  so  that  the  proboscis  becomes 
soiled.  The  flies  will  bite  sick  animals  as  well  as  healthy  ones,  — 
hence  the  possibility  for  the  transmission  of  an  infectious  blood  disease 
seems  to  exist.  It  is  regrettable  that  so  little  experimental  evidence 
is  at  hand ;  however,  anthrax  is  at  once  thought  of,  owing  to  the 
virulence  and  hardiness  of  the  causative  bacillus.^ 


Fig.  110.  — a  horsefly 
(Chrysops)  in  the  act 
of  oviposition.  Note 
also  an  egg  mass 
farther  down  on 
the  leaf.  (Photo  by 
Hine.)     X  1. 


1  Garman,  H.,  1910.  An  outbreak  of  gadflies  in  Kentucky.  Kentucky 
Agricultural  Exp.  Sta.,  Bull.  No.  151. 

2  Mr.  M.  B.  Mitzmain  has  verbally  informed  the  writer  (Feb.  17,  1914) 
that  he  has  successfully  transmitted  anthrax  from  artificially  infected  guinea 
pigs  to  healthy  guinea  pigs  through  the  agency  of  both  Tabanus  striatus  and 
Stomoxys  calcitrans.  A  preliminary  account  of  these  experiments  is  in  the  Journal 
of  Tropical  Medicine  and  Hygiene  (London),  Vol.  XVII,  No.  4. 


152        MEDICAL  AND   VETERINARY  ENTOMOLOGY 


Anthrax,  also  known  as  malignant  pustule  or  carbuncle,  wool  sorter's 
disease,  charbon  (French),  is  caused  by  Bacillus  anthracis.  Nearly  all 
species  of  domesticated  animals  and  man  are  susceptible ;  the  herbivora 
and  rodents  are  most  liable  to  infection.  The  mortality  may  be  as  high 
as  70  to  90  per  cent. 

After  the  introduction  of  the  organism  into  the  animal  the  incuba- 
tion period  is  exceedingly  short,  i.e.  from  three  to  six  days.  The  bacilli 
are  seen  in  the  blood  stream  in  advanced  cases  as  chains  of  rod-shaped 
bodies  (Fig.  111). 

Entrance  to  the  body  is  gained  mainly  in  one  ot  three  ways,  1st, 
through  lesions  or  pricks,  i.e.  inoculation,  producing  local  anthrax  or 

malignant  pustule ;  2d,  by  in- 
halation of  the  spores,  produc- 
ing pulmonary  anthrax ;  and  3d, 
by  ingestion  with  food,  producing 
intestinal  anthrax. 

Manifestly  horseflies  could 
only  relate  directly  to  the  first 
mode  of  infection  (inoculation), 
but  it  is  not  altogether  improb- 
able that  an  epidemic  of  an- 
thrax may  thus  be  started  and 
assisted  in  spreading.  Nuttall 
cites  Bollinger  (1874),  who  cap- 
tured horseflies  on  a  cow  dead 
from  anthrax  and  saw  the  bacilli 
in  preparations  made  from  the 
stomachs  and  intestines  of  the 
insects.  Two  rabbits  inoculated 
therewith  died  of  anthrax.  Of  course,  the  insects  would  have  to  be 
crushed  on  the  animal,  and  the  wound  produced  by  the  bite  thus  in- 
fected in  order  to  produce  the  disease. 

However,  many  instances  are  recorded  in  which  apparently  the 
simple  bite  of  the  fly  was  all  that  was  needed  to  produce  malignant 
pustule  in  humans.  Several  reputable  physicians  have  related  instances 
to  the  writer  in  which  this  was  said  to  have  occurred,  notably  one  case 
in  a  Western  state  in  which  a  man  was  in  the  act  of  burying  a  cow  dead 
of  anthrax  when  he  was  bitten  severely  in  the  back  of  the  neck  by  a 
horsefly  and  in  a  few  days  developed  a  malignant  pustule.  Nuttall  also 
cites  a  number  of  similar  instances. 

Relation  to  Surra.  —  Surra  is  a  highly  fatal  disease  of  horses  and 
other  susceptible  animals,  such  as  the  carabao,  which  latter  may  evidently 
become  chronic  carriers.  Guinea  pigs  and  monkeys  are  also  highly 
susceptible.  The  disease  is  endemic  in  the  Philippine  Islands,  southern 
Asia,  Korea  and  Madagascar.  The  causative  organism  is  Trypanosoma 
evansi  Steel  which  resembles  the  trypanosome  of  Nagana  very  closely, 


Fig.  111.  — Bacillus  anthracis,  causative  organ- 
ism of  anthrax.     (Greatly  enlarged.) 


BUFFALO  GNATS  AND   HORSEFLIES 


153 


as  do  the  symptoms,  i.e.  there 
is  fever,  oedema  of  the  abdo- 
men and  genitaha,  marked  de- 
pression and  emaciation.  The 
trypanosomes  are  found  in 
the  blood  and  especially  the 
lymph  swellings  from  the  be- 
ginning of  the  first  symptoms. 
The  incubation  period  is  from 
eight  to  nine  days. 

Mitzmain  ^  has  been  suc- 
cessful in  transmitting  the  dis- 
ease from  animal  to  animal 
through  the  agency  of  a  horse- 
jfly,  Tabanus  striatus  Fabr. 
(Fig.  112). 

In  a  series  of  experiments 
in  which  Tabanus  striatus  was 
used,  he  allowed  the  flies  to 
first  bite  an  infected  guinea 
pig  or  horse  for  not  more  than 
one  minute,  usually  forty-five 
seconds,  and  then  transferred 
them  to  a  healthy  animal 
where  they  were  allowed  to 
complete  the  meal  without  in- 
terruption. An  interruption 
of  five  seconds  to  three  min- 
utes was  necessary  to  transfer 
the  files  from  animal  to  ani- 
mal. The  horses  and  mule 
employed  in  these  experiments 
were  kept  in  a  screened  stable 
for  from  six  to  eight  months 
previous,  and  the  monkeys, 
guinea  pigs  and  rabbits  in 
fiy-screened  cages  for  about 
ninety  days.  In  all  cases  the 
animals  were  examined  fre- 
quently (blood  examinations 
made)  and  declared  surra  free 
at  the  time  the  experiments 
began. 

1  Mitzmain,  M.  B.,  1913.  The  mechanical  transmission  of  Surra  by  Ta- 
banus striatus  Fabricius.  PhiUppine  Journ.  of  Sci.,  Vol.  VIII,  No.  3,  Sec.  B,  pp. 
223-229. 


154        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

Flies  bred  from  eggs  were  allowed  to  bite  a  guinea  pig  which  had 
been  inoculated  with  blood  from  a  carabao  which  had  been  infected  with 
surra  for  nearly  a  year  previous  to  the  experiment.  Three  flies  were  ap- 
plied individually  in  tubes  to  the  surra-infected  guinea  pig  and  allowed 
to  feed  from  forty-five  seconds  to  one  minute  and  thirty  seconds,  after 
which  they  were  transferred  to  a  monkey  and  allowed  to  feed  until 
satisfied,  i.e.  from  five  to  twenty-one  minutes.  The  first  high  tempera- 
ture, 40.1°  C,  occurred  on  the  eleventh  day,  accompanied  by  a  few 
trypanosomes  in  the  peripheral  circulation,  increasing  in  numbers  until 
the  death  of  the  monkey  on  the  twenty-fifth  day. 

Blood  from  the  heart  of  this  monkey  was  inoculated  into  a  horse  and 
two  guinea  pigs.  The  latter  showed  infection  on  the  eighth  and  ninth 
days  respectively,  and  the  horse  on  the  seventh  day.  Two  flies  were 
permitted  to  bite  this  horse,  the  insects  being  interrupted  in  their 
biting  in  from  forty  to  forty-five  seconds  and  then  transferred  to  a 
healthy  horse  where  the  feeding  w^as  completed.  This  animal  showed 
numerous  trypanosomes  in  its  circulation  on  the  ninth  day.  Thus  posi- 
tive results  were  secured  in  both  a  monkey  and  a  horse. 

Blood  from  this  newly  infected  horse  was  inoculated  into  a  mule, 
two  monkeys  and  two  guinea  pigs,  all  of  which  became  infected  in  due 
season,  both  monkeys  dying  on  the  fourteenth  and  fifteenth  days  re- 
spectively. 

A  second  series  of  experiments  was  carried  on  with  captured  flies, 
which  w^ere  allowed  to  bite  the  above-mentioned  surra  horse  and  later  a 
healthy  horse,  similar  feeding  methods  being  observed.  This  experi- 
ment also  proved  positive,  as  did  blood  inoculations  to  monkeys  and 
guinea  pigs. 

In  order  to  eliminate  the  possibility  of  hereditary  transmission  of 
trj^panosomes  in  the  flies  a  further  experiment  was  conducted,  in  which 
seventy-four  flies,  hatched  from  eggs  of  a  fly  which  had  previous  to  egg 
deposition  fed  on  a  surra  monkey,  were  allowed  to  bite  a  healthy  monkey 
during  a  period  of  two  weeks  with  negative  results. 

Mitzmain  concludes  that  the  "  contaminated  labellum  of  the  fly  does 
not  appear  to  be  a  factor  in  the  conveyance  of  infection.  The  maximum 
length  of  time  that  TryjKinosoma  evansi  has  been  demonstrated  micro- 
scopically in  the  gut  of  this  species  of  fly  after  feeding  on  infected  blood 
is  thirty  hours ;  the  organisms  were  found  in  the  fly's  dejecta  two  and 
one  half  hours  after  biting  the  infected  animal ;  and  suspension  of  flies, 
when  injected  subcutaneously,  were  found  infective  for  animals  for  a 
period  of  ten  hours  after  the  flies  had  fed  on  infected  blood." 

In  a  letter  to  the  writer  under  date  of  Nov.  18,  191.3,  Mitzmain  states 
that  "  infection  is  not  transferred  by  Tabanus  striatus  later  than  twenty 
minutes  after  the  infective  meal.  The  longest  time  I  have  succeeded  in 
inducing  flies  to  transmit  was  fifteen  minutes  and  all  results  from  twenty 
minutes  to  forty-eight  hours  were  entirely  negative.  This  despite  the 
fact  that  trypanosomes  survive  in  the  intestinal  tract  of  T.  striatus  for 


BUFFALO  GNATS  AND   HORSEFLIES  155 

a  period  of  thirty  hours."  Mitzmain  believes  this  horsefly  to  be  the 
principal  carrier  of  surra  and  that  the  stable  fly,  Stomoxys  calcitrans,  is 
ruled  out,  which  is  indeed  indicated  by  the  long  and  careful  series  of 
experiments  conducted  by  that  worker  on  both  species  of  flies. 

Control.  —  Liasmuch  as  the  painful  bite  of  the  Tabanidse,  especially 
if  these  insects  are  abundant,  makes  the  life  of  domesticated  animals, 
notably  horses,  quite  unbearable,  it  is  desirable  that  some  repellent 
substance  or  mechanical  means  be  employed  to  prevent  injury,  Efla- 
cient  repellents  usually  contain  fish  oil,  which  is  disagreeable  and  in  the 
presence  of  dust  produces  a  very  filthy  coat ;  other  materials  in  use  are 
"  dips  "  and  these  do  not  as  a  rule  act  for  more  than  a  few  hours  at  most. 
Furthermore  where  whole  herds  of  animals  are  to  be  treated,  this 
method  is  impracticable.  Horse  nets  afford  considerable  relief,  and 
often  avert  dangerous  "  runaways." 

Comparatively  little  of  a  preventive  nature  has  been  done,  except 
for  the  notable  work  of  Porchinski,  reported  by  Howard.^  Porchinski 
observed  that  Tabanids  collect  in  great  numbers  in  the  neighborhood 
of  humid  spots  and  lower  themselves  to  the  surface  of  pools  to  drink, 
actually  touching  the  water  with  their  bodies.  It  occurred  to  him  that 
a  covering  of  kerosene  on  the  water  would  endanger  the  lives  of  the 
insects  as  they  came  in  contact  with  the  surface.  Hence  a  quantity  of 
kerosene  was  applied  to  a  given  pool,  with  most  gratifying  results.  By 
the  third  day  of  the  experiment  the  ''  pool  of  death  "  was  covered  with 
"  floating  islands  "  of  dead  Tabanids.  Porchinski  recommends  that  a 
favorite  pool  be  selected,  and  that  the  oil  be  poured  on  so  that  a  thick 
uniform  layer  of  oil  is  formed  covering  the  entire  pool.  Such  "  pools  of 
death  "  apparently  attract  the  Tabanids  from  over  a  considerable  adja- 
cent area.  The  oil  must  of  course  be  applied  as  early  as  possible  during 
the  season  when  the  adult  flies  appear  and  begin  to  mate  and  deposit 
eggs. 

Systematic.  The  following  description  of  family  characters  and 
key  to  the  North  American  Genera  is  according  to  Hine,^  our  highest 
authority  on  the  Tabanids. 

"The  family  Tabanidae  includes  medium-sized  to  large  insects  commonly 
called  horseflies,  gadflies,  deerflies,  dogflies,  earflies  and  various  other  names. 
Usually  its  members  are  readily  recognized  at  sight  by  their  form  and  general 
appearance. 

"The  three-jointed  antennae  with  the  third  joint  annulated  and  without  a 
style  or  arista,  the  rather  large  tegulse,  and  the  well-developed  pulviliform 
em  podia  taken  together  serve  to  distinguish  them  from  other  flies  in  case  of  any 
doubt. 

"None  of  the  species  are  really  small;  the  head  is  large,  larger  and  hemi- 
spherical in  the  male,  smaller  and  somewhat  flattened  in  the  female. 

1  Howard,  L.  O.,  1899.  A  remedy  for  gadflies.  Porchinski's  recent  dis- 
covery in  Russia,  with  some  American  observations.  U.  S.  Dept.  of  Agric, 
Div.  of  Entomology,  Bull.  20,  N.  S. 

2  Hine,  James  S.,  1903.  TabanidsB  of  Ohio.  Ohio  State  Academy  of  Science, 
Special  Papers,  No.  5. 


156        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

"The  antennae  are  porrect  and  composed  of  three  segments  of  which  the  third 
is  compound,  having  five  or  eight  annulations.  When  there  are  eight,  the  basal 
one  is  only  slightly  longer  than  the  others,  but  when  there  are  five,  the  basal  one 
is  much  longer  than  any  of  the  others,  often  longer  than  all  the  others  combined. 

"The  eyes  are  separated  in  the  female  and  contiguous  in  the  male.  They 
have  an  area  of  enlarged  facets  above  in  the  latter  sex,  and  in  life  are  marked 
with  green  and  purple  markings  m  both  sexes.  In  dry  specimens  these  mark- 
ings are  lo.st,  but  may  be  partially  restored  by  moisture.  Ocelli  are  present  in 
some  species  and  absent  in  others;  and  the  occiput  is  flat  or  concave.  The 
proboscis  projects  and  in  some  species  is  much  elongated;  the  maxillary  palps 
are  large  and  two  segmented. 

"The  thorax  and  abdomen  are  clothed  with  more  or  less  hair,  but  no  spines 
or  bristles.  The  wings  are  rather  large  and  encompassed  by  the  marginal  vein, 
two  submarginal  and  five  posterior  cells  present,  basal  cells  elongate,  anal  cell 
usually  and  sometimes  some  of  the  posterior  cells  closed.  Tegulse  always  promi- 
nent. Legs  ample ;  pul villi  moderate ;  empodia  developed  pulviliform ;  middle 
tibia  with  spurs  at  the  tip. 

"Abdomen  composed  of  seven  visible  segments,  broad,  never  constricted." 

KEY  TO  THE  NORTH  AMERICAN  GENERA  OF  TABANID^ 

(after  Hine) 

1 .  Hind  tibite  with  spurs  at  the  tip,  sometimes  small 2 

Hind  tibia  without  spurs 6 

2.  Third  segment  of  the  antenna  composed  of  eight  annuli,  the  first  of  which  is 

only  a  little  longer  than  the  following  ones 3 

Third  segment  of  the  antenna  composed  of  only  five  annuli,  the  first  of  which 
is  much  longer  than  any  of  the  following  ones ;  ocelli  present     ....     5 

3.  Front  of  female  narrow;   ocelli  present  or  absent;   fourth  posterior  cell  at 

least  open Pangonia 

Frontof  female  broad  with  a  large  denuded  callus;  ocelli  present      ...    4 

4.  Eyes  in  the  female  acutely  angulated  above ;  wing  in  both  sexes  with  a  dark 

picture Goniops 

Eyes  in  the  female  not  acutely  angulated  above  ;  wings  hyaline  in  both  sexes 

Apatolestes 

5.  Second  segment  of  the  antenna  about  half  as  long  as  the  first ;   ej^es  in  life 

with  numerous  small  dots Silvius 

Second  segment  of  the  antenna  as  long  or  but  little  shorter  than  the  first ; 
wings  with  a  dark  picture Chrysops 

6.  Third    segment   of  the   antenna  without,   or  with   a   rudimentary   basal 

process        7 

Third  segment  of  the  antenna  with  a  well  developed  basal  process    Tabanus  ^ 

7.  Front  of  female  as  broad  as  long,  the  callus  transverse  ....  Hcematopota 
Front  of  the  female  narrow       Diachlorv.s 

A  description  according  to  Hine  of  a  few  of  the  commoner  species  is 
here  included. 

(1)  Tabanus  atratus  Fabricius,  the  black  horsefly  (Fig.  113),  is  from  "16-28 
mm.  in  length.  The  male  and  female  of  this  common  species  are  easily  as- 
sociated as  they  differ  only  in  sexual  characteristics.  The  whole  insect  is 
uniformly  black  and  the  thorax  and  abdomen  in  well-preserved  specimens  are 
thinly  covered  with  a  whitish  dust  which  is  easily  rubbed  off  when  the  specimens 
are  not  properly  cared  for. 

*  Including  Atylotus  and  Therioplectes. 


BUFFALO   GNATS  AND   HORSEFLIES 


157 


"  It  cannot  be  confused  with  any  other  species  recorded,  but  the  smaller 
specimens  resemble  wiedernanni  very  closely.     The   wider  front,   the  longer 


Fig.   113. — The  black  horsefly  {Tabanus  atratus)  ;   male  at  left,  female  at  right. 

(Photo  by  Hine.) 


X  1.5. 


basal  process  of  the  third  antennal  segment  and  the  shape  of  the  frontal 
callosity,  which  is  square  in  wiedernanni  and  wider  than  high  in  atratus,  are  dis- 
tinctive characters.  Its  much  larger 
size  and  less  shining  color  distinguish 
it  from  luguhris." 

(2)  Tabanus  stygius  Say  is  the 
black-and-white  horsefly.  "Length 
20-22  mm.  Third  segment  of  the 
antennse  red  at  base,  blackish  at  apex, 
first  and  second  segments  and  palpi 
dark;  legs  black,  often  the  tibia  red- 
dish at  base ;  wings  j^llowish  brow-n 
with  posterior  border  approaching 
hyaline,  a  brown  spot  on  the  bifurca- 
tion of  the  third  vein,  also  the  trans- 
verse vein  closing  the  discal  cell 
margined  with  brownish;  abdomen 
uniform  black. 

"  Female  :  Thorax  dorsaUy  plainly 
whitish  poUinose  with  more  intense 
longitudinal  lines. 

"  Male  :  Thorax  dorsally  uniform 
grayish  brow^n  in  well-preserved  speci- 
mens." 

(3)  Tahanus  pimdifer  0.  S.  is  also 
a  black-and-white  horsefly  (Fig.  114) 
resembling  T.  stygius,  except  that  it 
has  the  front  tibia'  wdiite  on  the 
basal  third  and  the  thorax  uniformly 
white  in  both  sexes. 

(4)  Tabanus  costalis  Wied.,  the  green  head,  is  one  of  the  most-dreaded  stock 
pests.     "Length   12-14  mm.     Palpi   yellowish,    antenna?   brownish  with  the 


Fig.   114.  —  A  black-and-white  horsefly  (Ta- 
banus punctifer)  common  in  California.     X  2. 


158        MEDICAL  AND   VETERINARY  ENTOMOLOGY 


annulate  portion  darker;  thorax  including  the  scutelluin  uniformly  grajdsh 
yellow  pollinose ;  legs  largely  black,  base  of  front  tibite  and  the  middle  and 
hind  tibia?  except  at  apex  yellowish ;  wings  hj^aline  with  the  costal  cells  yellow- 
ish, veins  yellowish ;  abdomen  above  alternately  striped  with  black  and  grayish 
3^ellow. 

"  Female :  Frontal  callosity  black,  above  with  a  ver.y  much  narrowed  prolonga- 
tion, the  part  of  which  adjacent  to  the  callosity  is  sometimes  obliterated  leaving 
the  upper  part  as  a  separate  spot. 

"  Male  :  This  sex  is  much  like  the  female  and  easily  associated  with  it,  but  there 
is  a  tendency  toward  obliteration  of  the  distinct  markings  of  the  abdomen, 
the  black  of  the  female  is  replaced  by  brownish  and  the  stripes  may  blend  so 
that  the  whole  base  of  the  abdomen  is  practically  one  color." 

(5)  Tabanus  lineola  Fabr.,  the  lined  horsefly  (Fig.  115),  is  also  an  important 
stock  pest.  "Length  12-15  mm.  Palpi  white  ;  antenme  reddish,  annulate  por- 
tion of  third  segment  darker ;  thorax  brown 
and  gray  striped,  the  latter  color  not  promi- 
nent ;  wings  hyaline  ;  legs  reddish,  apex  of  the 
front  tibia  plainly,  apexes  of  middle  and  hind 
tibiae  faintly,  and  all  of  the  tarsi  dark  brown ; 
abdomen  above  brown  or  black  with  three 
prominent,  gray  stripes. 

The  males  and  females  of  this  species  are 
easily  associated.  In  the  latter  sex  there  is 
sometimes  a  confusion  of  colors ;  the  dark  is 
replaced  by  reddish  but  the  gray  mid-dorsal 
stripe  is  always  prominent  in  all  well-pre- 
served specimens." 

(6)  Tabanus  sulcifrons  Macq.  is  known  as 
the  autumn  horsefly.  "Length  18-21  mm. 
Palpi  brownish,  antennae  nearly  black  with 
the  third  segment  brownish  at  base;  legs 
dark,  bases  of  tibia?  darker ;  wings  with  a 
distinct  brownish  tinge,  cross  veins  at  the 
end  of  the  discal  cell  and  bifurcation  of  the 
third  vein  margined  with  brown. 

"  Female  :  front  with  parallel  sides,  fron- 
tal callosity  shining  brown,  not  quite  as  wide 
at  the  front,  nearly  square  and  with  a  linear 
prolongation  above.  Segments  of  the  abdomen  above  with  prominent  gray, 
hind  margins  which  expand  into  large  gray  triangles  in  the  middle ;  usually  a 
black  m.ark  on  the  anterior  part  of  each  of  the  second  and  third  segments  at  the 
apex  of  the  gray  triangle. 

"  Male  :  The  division  between  the  large  and  smaU  facets  of  the  eye  prominent ; 
head  slightly  more  convex  than  in  the  female  but  nearly  of  the  same  size,  colora- 
tion of  the  whole  body  the  same  as  in  the  female." 

(7)  Tabanus  striatus  Fabr.  (Fig.  112)  is  said  to  be  the  most  prevalent  horsefly 
of  the  Philippine  Islands,  and  is  known  to  be  an  important  carrier  of  Surra. 
The  following  description  is  after  Mitzmain  (loc.  cit.). 

"The  male  is  very  distinct  from  the  female,  being  smaller  and  having  a 
larger  head  and  different  color  markings. 

"The  distinctly  clavate  palpi  are  shorter  than  in  the  female,  only  two  thirds 
as  long  as  the  labium ;  they  are  dirty  white  and  fringed  with  moderately  long 
black  hairs. 

"The  abdominal  color  markings  take  the  form  of  a  T  of  pale  cadmium  yellow 
in  a  field  of  burnt  sienna,  bordered  with  pale  clay  yellow.  The  area  of  the  large 
facets  of  the  eyes  is  colored  Roman  sepia  surroimded  by  an  elliptical  band  of 


Fig. 


115.  —  The    "lined"    horsefly 
{Tabanus  lineola).       X  3. 


BUFFALO  GNATS  AND   HORSEFLIES  159 

ultra  ash  gray.  The  field  of  small  facets  has  a  mauve  fringe  bounding  an  area 
of  iridescent  mauve  and  Prussian  green. 

"Size  :   14  to  15  millimeters. 

"Wing  expanse :  25  to  28  millimeters. 

"Female:  The  front  is  narrow,  converges  slightly  anteriorly;  the  color  is 
golden,  mai'ked  with  a  black  callosity  of  irregular  form. 

"The  head  is  considerablj^  smaller  than  that  of  the  male;  eyes  iridescent 
mauve  and  Prussian  green. 

"The  palpi  are  prominently  conical,  as  long  as,  or  slightly  longer  than,  the 
labium ;  the  color  is  the  same  as  in  the  male,  mottled  with  short  black  hairs. 

"The  abdomen  is  alternately  striped  with  Cologne  earth  and  pale  clay  yellow. 
The  median  stripe  is  pale  claj^  yellow.  In  both  sexes  the  thorax  is  indistinctly 
striped  with  pale  clay  yellow  and  pale  brown,  and  the  wings  are  transparent 
except  the  costal  and  subcostal  cells  which  are  pale  brown. 

"Size  :   15  to  17  millimeters. 

"Wing  expanse :  26.5  to  29  millimeters." 


CHAPTER   XIII 


THE  COMMON  HOUSE   FLY 


Order   Diptera,   Family   Muscidce 
Life  History,  Habits  and  Epilation  to  Disease 

Family  Muscidae.  —  The  family  Muscidse,  to  which  the  house  fly 
{Musca  domestica  Linn.)  belongs,  has  the  following  characteristics : 
"  Rather  small  to  moderately  large,  never  elongate,  thinly  hairy  or  bare 
flies.  Antennal  arista  plumose  to  the  tip,  sometimes  above  only,  and 
rarely  bare,  in  which  cases  the  absence  of  bristles  on  the  abdomen, 
except  at  tip,  together  with  the  narrowed  first  posterior  cell,  characters 
distinctive  of  the  group,  will  distinguish  the  flies  belonging  here  from 

their  allies.  Eyes  of  the  male  ap- 
proximated or  contiguous ;  front 
of  female  broad.  Eyes  bare  or 
hairy.  Abdomen  composed  of  four 
visible  segments.  Genitalia  not 
prominent "  (Williston  ^) . 

Characterization  of  the  House 
Fly.  —  Hewitt's  ^  description  of  the 
house  fly  after  Schinir  is  undoubt- 
edly the  best  for  our  purpose,  viz. 
"  Frons  of  male  occupying  a  fourth 
part  of  the  breadth  of  the  head. 
V  Frontal  stripe  of  female  narrow  in 
front,  so  broad  behind  that  it  en- 
tirely fills  up  the  width  of  the  frons. 
The  dorsal  region  of  the  thorax 
dusty  gray  in  color  with  four 
equally  broad  longitudinal  stripes.  Scutellum  gray  with  black  sides. 
The  light  regions  of  the  abdomen  yellowish,  transparent,  the  darkest 
parts  at  least  at  the  base  of  the  ventral  side  yellow.-  The  last  segment 
and  a  dorsal  line  blackish  brown.  Seen  from  behind  and  against  the 
light  the  whole  abdomen  shimmering  yellow,  and  only  on  each  side  of 
the  dorsal  line  on  each  segment  a  dull  transverse  band.     The  lower 


Fig.   116.  —  The  common  house  fly  (Musca 
domestica  Linn.).       X  4. 


1  Williston,  S.  W.,  1896. 
Hathawa5%  New  Haven. 

2  Hewitt,  C.  Gordon,  1910. 
sity  Press,  Manchester,  England. 


Manual  of  North  American  Diptera.     James  T. 
The  House  Fly.    xiii  +  195  pp.     The  Univer- 


160 


THE   COMMON  HOUSE  FLY 


161 


part  of  the  face  silky  yellow, 
shot  with  blackish  brown. 
Median  stripe  velvety  black. 
Antennae  brown.  Palpi  black. 
Legs  blackish  brown.  Wings 
tinged  with  pale  gray  with  yel- 
lowish base.  The  female  has 
a  broad  velvety  black,  often 
reddishly  shimmering,  frontal 
stripe,  which  is  not  broader  at 
the  anterior  end  than  the 
bases  of  the  antennae,  but  be- 
comes so  very  much  broader 
above  that  the  light  dustiness 
of  the  sides  is  entirely  obliter- 
ated, the  abdomen  gradually 
becoming  darker.  The  shim- 
mering areas  of  the  separate 
segments  generally  brownish. 
All  the  other  parts  are  the 
same  as  in  the  male.  Mature 
insect  6-7  mm.  in  length,  IS- 
IS mm.  across  the  wings " 
(Fig.  116). 

Why  called  House  Fly.  — 
Out  of  a  total  of  23,087  flies 
collected  by  Howard  ^  in  din- 
ing rooms  in  different  parts  of 
the  country  22,808  or  98  per 
cent  of  the  whole  number  were 
Musca  domestica.  Again  out 
of  a  total  of  294  flies  collected 
by  the  writer,  representing  the 
entire  fly  population  of  one 
house,  202  or  94,4  pe^  cent 
were  Mnisca  domestica.  Thus 
the  term  common  house  fly  is 
not  misapplied.  Several  of 
the  commoner  species  of  flies 
found  indoors  are  shown  in 
the  accompanving  illustration 
(Fig.  117), 

Distribution  of  Sexes.  —  In 
order  to  determine  the  distribution  of  the  sexes,  observations  were  made 

^  Howard,  L.  O.,  1900.     A  Contribution  to  the  Study  of  the  Insect  Fauna  of 
Human  Excrement.     Proc.  Wash.  Acad,  of  Sciences,  Vol.  II,  Dec.  28,  pp.  541-604. 


162       MEDICAL  AND  VETERINARY  ENTOMOLOGY 

under  two  different  conditions,  viz.  first,  six  sweepings  with  an  insect 
net  were  made  over  a  horse-manure  pile  on  which  many  flies  had  gathered 
(the  results  are  shown  in  Table  VI) ;  second,  all  but  half  a  dozen  flies 
were  collected  in  one  house,  giving  a  fairly  representative  lot  for  in- 
doors, even  under  screened  conditions  (Table  VII). 

TABLE  VI 

Showing  Results  with  Regard  to   Sex  and  Species  in  Six  Sweepings 
FROM  A  Horse  Manure  Pile  on  May  19,  1909 


House  fly  {Musca  do- 
mestica)     .     .     .     . 

Muscina  sp.       .     .     . 

Blowfly    (Calliphora 
sp.)        

Lucilia  ccesar     .     .     . 

Other  species     .     .     . 

Totals 


First 


9 
153 
6 

2 
1 


12    126 


Second       Third 


8l|3 
70 

11 
10 
42 


? 

64 
5 

0 
1 
1 


946       71 


Fourth 


9     77 
2        5 


15      85 


Fifth 


d        ? 

4    210 
3      10 


11    222 


Sixth        Total 


d  'i 

5  112 

1  4 

1  0 
0  0 

2  0 


116 


? 
697 
37 


3        3 
0       4 

13 13 

56    754 


TABLE  VII 

Showing  Number  of   Individuals  Collected  in   a  Screened   Dwelling 
June  1,  1909,  Representing  the  Entire  Fly  Population  of  the  Same 

$  9 

House  fly  [Musca  domestica)       86  116 

Muscina  sp 3  1 

Homalomijia  sp 5  0 

Calliphora  sp _1_      2 

Totals 95  119 


Explanation  and  Comparison  of  Tables  VI  and  VII.  —  These  two 
tables  give  us  some  information  as  to  the  relative  abundance  of  the 
house  fly,  and  the  distribution  of  the  sexes.  Table  VI  shows  clearly  that 
of  those  flies  which  frequent  both  the  manure  pile  and  the  home,  the 
house  fly  (Musca  domestica)  composes  90  per  cent,  and  that  of  the  total 
collected,  over  95  per  cent  (95.4  per  cent)  were  females.  Thus,  it  is  clear 
that  it  is  the  "  instinct "  to  oviposit  (to  lay  eggs)  that  has  mainly  attracted 
these  insects  to  the  manure.  In  fact,  fresher  parts  of  the  manure  pile 
are  often  literally  white  with  house-fly  eggs  in  countless  numbers.  Ob- 
servations made  in  the  near  vicinity  of  the  manure  piles  proved  that 
certainly  the  same  percentage  (over  95  per  cent)  of  the  flies  clinging  to 
the  walls  of  the  stable,  boxes  and  so  on  were  males. 

That  the  number  of  males  and  females  in  the  house  fly  is  normally 
about  equal  is  evidenced  by  the  fact  that  of  a  total  of  264  pupse  collected 
indiscriminately  and  allowed  to  emerge  in  the  laboratory,  129  were  males 


THE   COMMON  HOUSE   FLY 


163 


and  135  were  females.  The  author  has,  however,  made  observations 
on  certain  flesh  flies,  Lucilia  ccesar  Linn,  and  Calliphora  vomitoria  Linn., 
which  indicate  that  the  factor  of  underfeeding  must  be  considered  in  this 
connection.  From  a  large  amount  of  unpublished  data,  it  is  evident 
that  underfeeding  results  in  the  emergence  of  a  greater  percentage  of 
males.  This  does  not  imply,  however,  that  sex  is  influenced  by  feeding ; 
it  only  indicates  that  cutting  short  on  food  supply  destroys  the  larval  fe- 
males first.  Feeding  experiments,  not  yet  complete,  on  the  house  fly 
indicate  that  the  same  holds  true  here,  but  also  that  this  insect  is  not  so 
plastic  as  the  flesh  fly,  hence  does  not  vary  so  greatly  in  size  and  dies 
more  easilv  when  underfed. 


■ 

• 

• 

J 

1  )|: 

_ 

: '. 

1 

Fig.   118.  —  Life  history  of  common  house  fly. 
(d)  imago  or  adult. 


(a)  eggs ;  (b)   larva ;  (c)  pupa ; 
X2. 


Of  the  total  number  of  house  flies  (202)  collected  indoors  (June,  1909), 
representing  all  but  perhaps  six  of  the  total  number  in  that  particular 
house,  57  per  cent  were  females,  showing  nearly  equal  distribution  for 
the  sexes.  This  would,  it  seems,  indicate  that  males  and  females  are 
equally  attracted  to  the  house  by  odors  issuing  therefrom. 

Life  History.  —  The  house  fly  passes  through  a  complex  metamorpho- 
sis (Fig.  118),  i.e.  egg,  larva  (maggot),  pupa  (resting  stage)  and  imago 
or  full-grown  winged  insect. 

From  75  to  150  eggs  are  deposited  singly,  piling  up  in  masses,  and  there 
are  usually  several  (2  to  4)  such  layings  at  intervals  of  three  or  four  days. 
Female  flies  begin  depositing  eggs  from  nine  to  twelve  days  after  emerg- 
ing from  the  pupa  case.  Excrementous  material,  especially  of  the  horse 
(Figs.  119-120),  is  the  favorite  material  upon  which  the  eggs  are  deposited 
and  upon  which  the  larvae  feed.     Other  suitable  situations  are  kitchen 


164       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

refuse,  brewer's  grain  and  other  decaying  vegetable  matter.     Where  the 
city  garbage  is  carefully  disposed  of  with  only  ordinary  attention  to  horse 


Fig.    119.  —  A  typical  rural  fly  breeding  place,  —  the  everlasting  manure  pile.     The  prin- 
cipal menace  is  the  fresh,  warm  manure  added  on  top  daily. 


Fig.  120.  —  Fly  maggot.s  will  be  found  in  abundance  in  similar  manure  piles.  This  is 
surely  not  sufficiently  ornamental  to  maintain  indefinitely,  nor  will  it  improve  the 
health  of  the  neighbors. 


manure,  it  seems  quite  safe  to  say  that  95  per  cent  of  the  house  flies  are 
bred  in  the  latter.  The  house  fly  does  not  breed  as  abundantly  in  cow 
manure,  although  plentifully  enough  to  take  such  material  into  con- 


THE   COMMON  HOUSE   FLY  165 

sideration,  especially  when  it  occurs  in  piles  mixed  with  straw.  The 
eggs  of  the  house  fly  hatch  in  from  twelve  to  twenty-four  hours;  the 
newly  hatched  larva?  begin  feeding  at  once  and  grow  rapidly. 

To  gain  an  estimate  of  the  number  of  larvae  developing  in  an  average 
horse-manure  pile,  samples  were  taken  after  four  days'  exposure  to  flies, 
with  the  following  results  :  first  sample  (4  lbs.)  contained  6873  larvae  ;  sec- 
ond sample  (4  lbs.),  1142;  third  sample  (4  lbs.),  1585;  fourth  sample  (3 
lbs.),  682  ;  total  10,282  larvae  in  15  pounds.  All  of  the  larvae  were  quite 
or  nearly  full  grown.  This  gives  an  average  of  685  larvae  per  pound. 
The  weight  of  the  entire  pile  was  estimated  at  not  less  than  1000  pounds, 
of  which  certainly  two  thirds  was  infested.  A  little  arithmetic  gives  us 
the  astonishing  estimate  of  455,525  larvae  (685  X  665),  or  in  round  num- 
bers 450,000,  i.e.  about  900,000  larvae  per  ton  of  manure  afta*  only  four 
days'  standing.  This  particular  manure  pile  (not  from  a  livery  stable, 
either)  was  only  one  of  many  known  to  exist  in  various  parts  of  the  city. 
No  wonder  flies  fairly  swarm  in  the  vicinity  of  these  choice  ornaments  ! 

The  larval  stage  is  the  growing  period  of  the  fly,  and  the  size  of  the 
adult  will  depend  entirely  upon  the  size  that  the  larva  attains.  An 
underfed  larva  will  result  in  an  undersized  adult.  The  growing  stage 
requires  from  four  to  six  days,  after  which  the  maggots  often  crawl 
away  from  their  breeding  place,  many  of  them  burrowing  into  the  loose 
ground  just  beneath  the  manure  pile,  or  under  boards  or  stones,  or  into 
dry  manure  collected  under  platforms  and  the  like.  (One  and  three 
fourths  pounds  of  dry  manure,  taken  from  beneath  a  platform,  contained 
2561  pupae).  The  larvae  often  pass  three  or  four  days  in  the  prepupal 
or  migrating  stage  before  actually  pupating ;  but  in  a  given  set  of  in- 
dividuals under  similar  conditions  the  various  stages  are  remarkably 
similar  in  duration,  —  when  one  pupates,  the  rest  will  certainly  follow 
in  short  order,  and  when  one  emerges,  others  quickly  appear.  The  aver- 
age time  required  for  development  from  the  egg  to  the  imago  is  differently 
estimated  by  various  observers,  inasmuch  as  temperature  greatly  in- 
fluences the  time  required.  Packard  (1874)  gives  the  time  at  from  ten 
to  fourteen  days,  Howard  (1906),  at  Washington,  D.C.,  as  ten  days.  In 
Berkeley,  California,  where  the  weather  is  uniformly  cool  (rarely  above 
80°  F.  and  a  mean  of  48°  F.  during  the  winter  months),  the  life  cycle 
is  completed  usually  in  from  fourteen  to  eighteen  days,  less  often  in 
twelve  days.  At  a  maintained  temperature  of  30°  C.  the  minimum 
time  required  for  complete  metamorphosis  is  nine  and  one  third  days. 
Prolonged  cool  weather  or  artificially  cooled  environment  results  in 
greater  retardation.  Even  allowing  for  such  retardation,  the  number  of 
generations  produced  during  the  summer  is  quite  large,  and  in  California 
(Berkeley)  I  have  seen  house  flies  emerging  from  their  breeding  places 
during  every  month  of  the  winter  season.  This  latter  fact  lends  even 
greater  importance  to  a  house-fly  campaign.  In  early  March  a  veritable 
pest  of  flies  was  encountered  while  on  a  trip  through  the  Imperial 
Valley  (California). 


166 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


Fig.  121.  —  Illustrating 
the  effect  that  under- 
feeding the  larva  has 
on  the  size  of  the 
adult  fly  (Lucilia  cce- 
sar).  Overfeeding,  if 
it  does  not  result  fa- 
tally, does  not  increase 
the  size  of  the  fly  over 
the  optimum,  as  may 
be  seen  by  the  upper- 
most individual,  which 
is  the  same  size  as  the 
next  lower  individual 
or  optimum.  Each  of 
the  next  lower  individ- 
uals is  the  result  of  de- 
creasing the  time  of 
feeding  by  six  hours. 
These  results  are  based 
on  a  large  number  of 
individuals  in  each 
case.      X  1. 


When  the  fly  emerges  from  the  pupa  case  with 
fully  developed  wings,  it  is  as  large  as  it  will  ever 
be,  except  in  expansion  and  addition  in  weight, 
due  to  stomach  contents  or  development  of  eggs 
in  the  female.  This  explains  why  no  young  house 
flies  are  seen  (young  in  the  sense  of  being  small). 
The  little  flies  upon  the  windows  are  not  "  baby  " 
flies,  but  belong  to  another  species,  also  adult. 
One  can  easily  influence  the  size  of  a  fly  by  un- 
derfeeding it  in  the  larval  stage,  as  illustrated  in 
Fig.  121  (see  Herms,^  1907).  The  question  has 
been  asked,  "  Why  are  all  house  flies  so  nearly  of 
one  size?"  This  is  not  altogether  true.  There 
are  some  undersized  house  flies,  but  the  great 
majority  of  the  larvse  or  maggots  find  ample  food 
for  optimum  development.  Furthermore,  experi- 
ments show  that  the  house  fly  is  not  as  plastic  in 
respect  to  food  conditions  as  the  flesh  fly ;  in  other 
words,  larvse  which  are  underfed  perish  easily. 

House  flies  reach  sexual  maturity  in  three  or 
four  days  and  begin  to  deposit  eggs  on  the  ninth 
day  after  emergence  from  the  pupa.  Sunshine 
stimulates  their  breeding  habits. 

Estimating  that  one  adult  fly  deposits  from 
120  to  150  eggs  with  at  least  six  lots  at  intervals 
of  from  three  to  four  days,  Hodge  ^  gives  us  the 
following  astounding  statement:  "A pair  of  flies 
beginning  operations  in  April  may  be  progenitors, 
if  all  were  to  live,  of  191,010,000,000,000,000,000 
flies  by  August.  Allowing  one  eighth  of  a  cubic 
inch  to  a  fly,  this  number  would  cover  the  earth 
47  feet  deep." 

Influence  of  Temperature  on  Life  History.  — 
While  conducting  an  extensive  series  of  experi- 
ments in  which  many  hundreds  of  house  flies 
were  used  in  all  stages,  a  record  was  made  of  the 
temperature  at  which  the  containers  were  kept. 
Ordinarily  not  more  than  one  to  three  quarts  of 
manure  were  used  for  the  growing  maggots,  hence 
the  temperature  of  the  environment  did  not  differ 
widely  from  that  of  the  manure.     The  temperature 


""  1  Herms,  W.  B.,  1907.  An  Ecological  and  Experi- 
mental Study  of  Sareophagidae.  Journ.  Exp.  Zoo!.,  Vol. 
IV,  No.  1,  pp.  45-83. 

2  Hodge,   C.   F.,   1911.     Nature  and  Culture,  July, 
1911. 


THE   COMMON   HOUSE   FLY 


167 


of  an  average  manure  pile  to  which  material  is  added  daily  varies 
from  18°  C.  to  6(3°  C.  Young  growing  larvse  are  most  numerous  at  tem- 
peratures varying  from  45°  to  55°.  Below  45°  half-grown  and  full-grown 
larvse  occur  and  above  55°  the  temperature  seems  to  become  too  great. 
From  the  following  table  it  will  be  seen  that  temperature  influences 
the  time  required  for  the  development  from  egg  to  imago  very  materially, 
but  nevertheless  with  an  average  outdoor  temperature  of  18°  C.  flies 
ordinarily  require  only  from  tw^elve  to  fourteen  days  to  pass  through 
the  same  stages ;  this  is  of  course  due  to  the  higher  temperature  of 
the  manure  pile,  as  already  indicated  above.  The  shortest  time  required 
for  complete  metamorphosis  is  seen  to  be  nine  and  one  third  days. 


TABLE  VIII 

Showing  Influence  of  Temperature  on  the  Length  of  Life  History 
of  musca  domestica 

The  insects  were  kept  at  the  temperature  indicated  from  egg  to  emergence 
of  the  imago.  The  average  temperature  is  here  given,  the  variation  from 
the  a\'erage  was  probably  not  more  than  ±  1°.  Temperature  of  the  air 
and  not  of  the  manure  is  here  considered.  - 


16°  C 

18°  C 

20°  C 

25*  C 

30°  C 

Min. 

Max. 

Min. 

Max. 

Min. 

Max. 

Min. 

Max. 

Min. 

Max. 

Egg  stage  .     .     . 

Larval  stage    .     . 

Pupa  stage      .     . 

Total      time     re- 
quired from  egg 
to  imago      .     . 

36    hrs. 
11    ds. 
18    ds. 

40  J  ds. 

40    hrs. 
26    ds. 
21    ds. 

481  ds. 

27    hrs. 
10    ds. 
12    ds. 

23J  ds. 

30    hrs. 

14  ds. 

15  ds. 

30i  ds. 

20    hrs. 

8    ds. 

10    ds. 

181  ds. 

30    hrs. 

10  ds. 

11  ds. 

22i  ds. 

12    hrs. 
7    ds. 

7    ds. 

14i  ds. 

20    hrs. 

8  ds. 

9  ds. 

17i  ds. 

8  hrs. 
5    ds. 
4    ds. 

9  Ids. 

12    hrs. 
6    ds. 
5    ds. 

11 1  ds. 

Average  time  re- 
quired   to    de- 
velop from  egg 
to  imago .    .     . 

44.8  days 

26.7  days 

20.5  days 

16.1  days 

10.4  days 

Other  Breeding  Places.  • —  Stable  yards  and  empty  town  lots  used  for 
horses  are  often  a  source  of  many  flies.  Here  the  droppings  from  the 
horses  accumulate  and  are  kept  moist  by  urine,  thus  affording  good 
breeding  places  (Fig.  122).  The  stable  yard  and  toum  lot  used  for  horses 
must  not  he  overlooked  in  the  campaign  against  the  house  fly.  Merely 
sweeping  up  the  manure  wath  a  broom  after  the  removal  of  the  manure 
pile  or  superficial  shoveling  without  scraping  up  the  loose  earth  will  not 
remedy  the  matter  entirely.  It  must  be  borne  in  mind  that  when  the 
larvae  have  fed  sufficiently  for  full  growth,  that  is,  from  four  to  five  days, 
they  crawl  into  the  loose  earth  underneath  the  manure  pile  (often  great 
pockets  of  larvse  may  be  found  thus),  or  they  wander  to  loose  debris  in 
the  immediate  vicinity ;  many,  of  course,  remain  in  the  drier  portions 
of  the  manure  pile  to  complete  their  life  cycle.     Thousands  of  pupae 


168        MEDICAL  AND  VETERINARY  ENTOMOLOGY 

(recognized  as  chestnut-colored,  barrel-shaped  objects)  were  taken  by 
the  writer  in  one  instance  from  beneath  a  platform  leading  into  a 
stable.  Therefore,  when  cleaning  up,  such  conditions  and  situations 
must  also  be  taken  into  account. 

Human  excrement,  if  left  uncovered,  furnishes  another  good  breeding 
ground  for  the  house  fly.  Indiscriminate  defecation  in  alley  ways  and 
out-of-the-way  places  should  be  considered  a  misdemeanor  punishable  by 
a  heavy  fine,  for  the  reason  that  house  flies  may  breed  in  human  excre- 
ment, and  especially  because  of  the  very  great  danger  of  disease  transmis- 
sion by  the  flies.  In  communities  where  there  is  no  sewer  system,  sanitary 
fly-tight  privies  should  be  required  by  ordinance  (see  next  chapter). 

Where  dairy  cattle  are  fed  on  brewer's  grain  the  waste  is  usually 


Fig.   122.  —  A  manure-covered  corral  kept  moist  by  urine  from  the  horses  forms  an  im- 
portant breeding  place  for  both  house  flies  and  stable  flies. 

thrown  away  in  small  heaps  in  a  near-by  field,  thus  affording  a  famous 
breeding  place  for  flies.  The  writer  has  found  that  such  conditions 
often  explain  the  great  abundance  of  flies  about  certain  certified  dairies, 
otherwise  in  excellent  condition.  All  wastes  of  this  kind  should  be 
spread  out  thin  so  that  the  material  dries  out  quickly,  thus  preventing 
the  development  of  flies. 

Guinea  pig  pens,  rabbit  pens  and  chicken  coops  may  become  prolific 
breeders  of  flies  if  they  are  not  carefully  cleaned. 

Kitchen  refuse  (Fig.  123),  decaying  fruit,  garbage  dumps,  in  fact 
any  organic  material  that  is  beginning  to  decompose,  — ■  all  afford 
breeding  places  for  the  house  fly.  But  the  source  of  the  fly  as  a  real 
nuisance  is  essentially  the  horse-manure  pile. 


THE   COMMON  HOUSE   FI.Y  169 

Range  of  Flight.  —  Ordinarily  under  city  conditions  it  may 
be  safely  said  that  where  flies  are  abundant  they  have  been  bred 
in  the  same  city  block  or  one  immediately  adjacent.  The  house 
fly  can,  however,  use  its  wings  effectively  and  may  be  carried  by 
the  wind,  though  it  usually  seeks  protection  very  quickly  when  a  strong 
breeze  blows.  Where  houses  are  situated  close  together  flies  have  the 
opportunity  to  travel  considerable  distances  by  easy  flights  and  they 
are  often  carried  on  meat  and  milk  delivery  wagons,  animals,  etc. 

In  a  most  illuminating  experiment  by  Copeman  ^  et  al,  it  has  been 
shown  that  house  flies  may  invade  a  community  at  a  distance  of  from  300 
yards  to  17,000  yards  from  their  breeding  place ;  in  this  case  a  refuse  heap. 

Longevity  of  Flies.  —  In  order  to  determine  the  longevity  of  flies 


Fig.    123.  —  A  poor   excuse   for  a  fly-tight   garbage  can.     This   should    be  regulated   by 

nrdinance. 


ordinance 

it  is  necessary  to  keep  the  same  individual  under  observation  from  the 
time  of  emergence  from  the  pupa  to  the  time  of  death.  The  writer  has 
done  this  by  keeping  each  pupa  in  a  separate  vial,  noting  the  time  of 
emergence  to  the  hour  and  spotting  each  fly  lightly  with  Chinese  white 
dorsallv  on  the  thorax.  The  spots  can  be  arranged  singly  and  in  com- 
bination so  that  many  different  flies  can  be  kept  under  observation  at 
the  same  time.  After  marking,  the  flies  were  liberated  m  bobbinet- 
covered  cages  (size  of  cages  never  more  than  8"  X  10"  X  18")-  Each 
cage  was  provided  with  sugar  water  and  a  receptacle  of  horse  manure. 
A  full  set  of  experiments  under  sufficiently  varying  conditions  indicate 
an  average  life  of  close  to  thirty  days  with  a  maximum  life  of  something 

1  Copeman,  Hewlett  and  Merriman,  1911  In  reports  to  .tli\local  Govern- 
ment Board  of  Public  Health  and  Medical  Subjects.  New  Series  No.  53,  Report 
No.  4  on  Flies  as  Carriers  of  Infection  (London). 


170        MEDICAL  AND  VETERINARY  ENTOMOLOGY 

over  sixty  days  during  the  summer  months.  In  hibernation  flies  may 
hve  over  winter,  i.e.  from  October  to  April,  which  is  the  case  in  our 
Eastern  and  Central  states.  In  California,  flies  emerge  from  their 
pupa  cases  throughout  the  winter,  and  their  life  history  is  then  con- 
siderably longer  than  in  summer. 

Dusting  flies  with  foreign  substances  for  longevity  experiments  is  not 
satisfactory,  inasmuch  as  they  easily  succumb  to  its  effects  or  are  cer- 
tainly'not  normal. 

Relation  to  Light.  —  In  determining  methods  of  control  the  normal 
behavior  of  organisms  under  natural  stimuli  should  be  taken  into  ac- 
count and  applied  wherever  possible.  The  better  acquainted  we  are  with 
the  normal  behavior  of  any  organism,  including  the  life  history,  the 
better  able  are  we  to  cope  with  it. 

The  larvse  of  the  house  fly  when  normal  respond  negatively  to  light 
upward  of  .00098  C.  M.,  i.e.  crawl  away  from  the  source  of  light  and  into 
darker  areas.  This  reaction  is  useful  to  the  larvae  because  light  and  its 
heating  or  desiccating  effect  is  injurious  both  directly  and  indirectly,  — 
the  latter  because  sunlight  dries  out  the  food  material  (manure)  unless 
heaped  up,  and  dry  manure  is  unfavorable  for  the  growth  of  the  larvae. 

On  the  other  hand,  the  adult  flies  respond  positively  to  light,  going 
toward  the  source  of  light.  This  reaction  is  less  pronounced  in  the 
females,  as  may  be  seen  from  the  following  table  (Table  IX). 

TABLE  IX 

Showing  the  Response  of  Adult  House  Flies  to  Light,  under  Various 

Intensities 

The  source  of  light  in  all  cases  was  an  incandescent  lamp ;  the  several  inten- 
sities were  secured  by  means  of  diaphragms  in  a  low-intensity  ^dark  box 
such  as  has  been  described  by  the  author  {loc.  cit.  1911). 


Sex 

No.  op 
Trials 

Average 
Time  Re- 
quired roR 
Response 

Per  Cent 
OP  Re- 
sponses 

UNDER 

Three 
Seconds 

Character  of 
Response 

Percentage 

Tow- 
ard 

Away 

Indiff. 

Reactions 

256  C.  M. 
.2533  C.  M. 
.2533  C.  M. 
.0633  C.  M. 

both 
male 
female 
both 

25 
50 
50 
50 

55.4    sec. 

8.86  sec. 

25.44  sec. 

24.68  sec. 

32% 
62% 
50% 
26% 

19 

58 
44 
41 

6 
2 
2 
3 

0 
0 
4 

6 

76% 
97% 
88% 
82% 

From  the  above  table  it  must  be  concluded  that  the  house  fly  responds 
positively  to  light  (goes  toward  the  source  of  light),  even  in  very  low  in- 
tensities, at  least  as  low  as  .0055  C.  M.  and  that  the  male  is  far  more  re- 
sponsive to  this  stimulus  than  is  the  female. 

The  female  is  less  reactive  to  light  and  more  reactive  to  chemical 


THE   COMMON   HOUSE   FLY  171 

stimuli  such  as  odors,  which  enable  her  to  find  the  proper  place  for  the 
deposition  of  eggs  and  food  for  the  larvae.  Because  of  the  more  or  less 
pronounced  relation  to  light,  manures  deposited  in  dark  places  are  less 
likely  to  breed  flies.  Flies  can  commonly  be  observed  coming  to  rest 
in  sunny  spots  in  preference  to  shade,  shunning  the  shadows. 

Large  areas  of  light  are  always  preferred  to  small  areas  of  light  even 
though  the  intensity  is  the  same.  The  following  experiment  is  evidence. 
Two  areas  of  light  with  a  ratio  of  1 :  3000  and  a  light  intensity  of  7.25 
candle  meters  were  placed  opposite  each  other  at  a  distance  of  one  meter, 
the  experimental  room  being  otherwise  completely  darkened  and 
painted  dead  black.  Fifty  flies  were  tested,  giving  each  fly  five  trials 
midway  between  the  light  areas.  Out  of  250  trials  149  were  toward  the 
larger  area,  93  toward  the  lesser  and  8  were  indifferent,  i.e.  59.6  per  cent 
toward  the  larger.  This  experiment  shows  that  the  flies  respond  posi- 
tively to  light  and  select  the  larger  area  by  preference.  Whether  this 
indicates  a  degree  of  image-forming  powers  or  not  need  not  be  con- 
sidered here,  but  the  writer  ^  has  found  that  certain  flesh  flies  also  re- 
spond more  readily  to  the  larger  area,  that  is  a  response  of  74  per  cent, 
and  Cole  ^  found  that  the  mourning  cloak  butterfly  shows  a  response  of 
87.2  per  cent. 

The  response  to  light  can  be  made  use  of  in  a  practical  way,  flrst  by 
placing  the  stable  manures  in  which  the  flies  breed  in  darker  portions  of 
the  stable  so  that  the  light  reactions  of  the  flies  will  take  them  away 
from  the  manure  and  toward  the  source  of  light;  secondly,  manure 
boxes  should  be  so  constructed  that  flies  finding  their  way  into  the  box 
or  developing  therein  are  afforded  an  opportunity  to  fly  toward  a  light 
opening  which  leads  into  a  fly  trap. 

Economic  Considerations.  —  Aside  from  the  loss  of  life,  through 
typhoid  fever  and  diseases  carried  wholly  or  in  part  by  the  fly,  an  economic 
loss  of  importance,  the  annual  loss  to  civilized  man  through  the  direct 
agency  of  the  house  fly  must  reach  astonishing  proportions.  Dr.  L.  O. 
Howard  estimates  the  cost  of  screening  at  over  ten  millions  of  dollars 
per  annum  for  the  United  States,  and  the  writer  has  estimated  the  cost 
of  fly  traps,  sticky  fly  paper  and  fly  poison  at  more  than  two  millions  of 
dollars  annually.  If  this  enormous  amount  were  spent  during  only  one 
year  in  controlling  the  fly  at  the  right  end  of  its  life  history,  a  second 
year  would  find  a  saving  of  several  millions  of  dollars,  not  to  mention 
the  lives  that  have  been  spared  and  the  comfort  wrought. 

Relation  to  Disease.  —  We  should  be  familiar  with  the  actual  method 
of  disease  transmission  by  the  house  fly.  Some  insects,  as  already 
described,  act  as  intermediate  host  for  pathogenic  organisms,  which 

1  Herms,  W.  B.,  1911.  The  Photic  Reactions  of  Sarcophagid  Flies,  es- 
pecially Lucilia  ccesar  Linn,  and  Calliphora  vomitoria  Linn.  Journ.  Exp.  Zool., 
Vol.  X,  No.  2,  pp.  167-226. 

^  Cole,  Leon  J.,  1907.  An  experimental  study  of  the  image-forming  powers 
of  various  types  of  eyes.  Proe.  Amer.  Acad.  Arts  &  Sci.,  Vol.  42,  No.  16,  pp. 
335-417. 


172       MEDICAL  AND  VETERINARY  ENTOMOLOGY 

latter  cannot  exist  sexually  and  be  transmitted  without  the  insect,  e.g. 
the  malarial  fever  parasite  (Plasmodium  vivax  and  other  species),  which 
passes  part  of  its  life  history  in  the  body  of  the  Anopheles  mosquito. 
The  house  fly,  as  far  as  known,  is  not  an  intermediate  host  necessary  to 
the  life  of  a  pathogenic  organism  of  humans,  but  is  by  accident  of  habit 


Fig.   124.  —  Head  of  the  common  house  fly,  front  view.      (Much  enlarged.) 


and  structure  one  of  the  most  important  and  dangerous  of  disease-trans- 
mitting insects.  In  habit  the  house  fly  is  revoltingly  filthy,  feeding 
indiscriminately  on  excrement  of  all  kinds,  on  vomit  and  sputum,  and 
is,  on  the  other  hand,  equally  attracted  to  the  daintiest  food  of  man, 
and  will,  if  unhindered,  pass  back  and  forth  between  the  two  extremes. 


THE   COMMON  HOUSE   FLY  173 

The  house  fly's  proboscis  (Fig.  124)  is  provided  with  a  profusion  of  fine 
hairs  which  serve  as  collectors  of  germs  and  filth ;  the  foot  (Fig.  125) 
of  the  fiy  when  examined  under  the  microscope  presents  an  astonishing 
complexity  of  structure.  Each  of  the  six  feet  is  equally  fitted  with  bristly 
structures  and  pads,  which  latter  secrete  a  sticky  material,  adding  thus 
to  the  collecting  powers.  This  structural  condition,  added  to  the  natural 
vile  habits  of  the  house  fly,  completes  its  requirements  as  a  transmitter 
of  infectious  diseases  of  certain  types. 

This  creature  has  long  been  known  to  contaminate  food,  but  has, 
nevertheless,  been  regarded  as  a  scavenger,  and  thus  as  a  real  servant 


Fig.   125.  —  Foot  of  the  common  house  fly.     (Much  enlarged.) 

of  man ;  but  if  there  remains  any  doubt  in  the  mind  of  the  reader,  aftw 
reading  what  follows,  as  to  the  necessity  of  getting  rid  of  this  wolf  in 
sheep's  clothing,  let  him  take  the  time  to  make  a  few  careful  observations 
for  himself. 

Circumstantial  evidence  against  the  house  fly  as  a  transmitter  of 
such  infectious  diseases  as  typhoid  fever,  tuberculosis,  dysentery  and 
cholera,  is  complete  as  summed  up  thus:  First,  it  possesses  the  best 
possible  structures  for  the  conveyance  of  "  germs  "  and  filth;  second, 
it  possesses  the  habit  of  feeding  on  excrement,  vomit  and  sputum  ;  third, 
the  causative  organisms  ("  germs  ")  of  the  above-named  diseases  may 
be  present  in  the  matter  mentioned  in  the  second  clause ;  fourth, 
the  house  fly  is  the  principal  fly  found  in  dwellings,  alighting  on  the 
prepared  food  of  man,  or  on  food  products  in  grocery  stores,  fruit  stands 
and  meat  markets.    > 

Experimental  evidence  that  the  house  fly  actually  does  carry  bacteria 
on  its  mouth  parts  and  feet  and  in  its  intestinal  tract  is  not  wanting. 
To  illustrate,  the  following  simple  experiment  may  be  cited. 


174       MEDICAL  AND  VETERINARY  ENTOMOLOGY 


In  order  to  show  that  the  house  fly  {Musca  domestica)  can  carry 
"  germs  "  of  a  known  kind,  a  partially  sterilized  fly  was  placed  in  a  test 
tube  containing  a  culture  of  Staphylococcus  aureus.  After  walking  about 
in  this  tube  and  becoming  contaminated  with  the  Staphylococci,  the  fly 
was  transferred  to  a  sterile  agar-agar  plate  upon  which  it  was  allowed  to 
crawl  about  for  three  minutes.  The  plate  was  then  incubated  for  twenty- 
four  hours,  after  which  it  was  examined  and  photographed  (Fig.  126). 
The  photograph  shows  the  trail  of  the  fly  as  it  had  walked  about. 

Every  place  that  the 
foot  touched  is  plainly 
marked  by  a  vigorous 
bacterial  growth. 
That  the  fly  cannot 
easily  get  rid  of  all 
the  bacteria  on  its 
feet  is  also  illustrated 
by  this  photograph, 
inasmuch  as  three 
minutes  spent  crawl- 
ing about  on  the  agar 
plate  did  not  appar- 
ently lessen  the 
growth-vigor  of  bac- 
teria deposited,  and  a 
second  plate  of  agar- 
agar  contaminated  by 
the  same  fly  immedi- 
ately after  exposure 
of  the  first  plate  gave 
equally  astonishing 
results.  The  same 
experiment  was  per- 
formed, using  Bacillus  prodigeosus  with  even  more  pronounced  results. 
These  experiments  were  repeated  several  times  with  like  effect. 

A  second  series  of  experiments  was  carried  on  as  follows :  During 
the  middle  of  May  (1909)  house  flies  were  captured  in  various  parts 
of  Berkeley,  placed  at  once  in  sterilized  vials,  and  in  the  laboratory 
placed  under  bell  jars  with  agar-agar  plates,  all  under  sterilized  con- 
ditions. After  the  flies  had  crawled  about  on  the  culture  media,  the 
latter  were  incubated  for  twenty-four  hours.  In  every  case  but  one 
a  strong  growth  of  bacteria  appeared.  This  one  was  incubated  longer 
and  after  forty  hours  four  centers  of  infection  appeared.  This  fly  had 
been  taken  on  a  sunny  wall  on  one  of  the  main  streets,  and  having 
been  under  observation  in  this  position  for  a  long  time  (as  reported  by 
the  assistant)  it  was  first  supposed  that  the  action  of  the  sunlight  had 
sterilized  it.     This  series  of  experiments  included  flies  taken  from  a 


Fig.  126.  —  Cultures  of  Staphylococcus  aureus  transferred 
by  a  house  fly  to  a  sterile  agar-agar  plate  upon  which  it 
was  allowed  to  crawl  for  three  minutes.  Incubation 
period,  24  hours. 


THE   COMMON  HOUSE   FLY  175 

number  of  situations,  namely,  principal  thoroughfares,  sunny  walls, 
street  corners,  manure  piles  and  the  dining  room.  Without  excep- 
tion the  flies  were  laden  with  bacteria,  and  in  all  cases  the  greatest  care 
was  exercised  not  to  introduce  accidental  infection  to  the  culture  plates. 

Probably  the  most  accurate  study  of  these  factors  was  carried  on 
by  Esten  and  Mason  ^  on  the  Sources  of  Bacteria  in  Milk  and  certainly 
most  striking  facts  were  revealed.  The  following  table  (Table  X)  and  at- 
tached remarks  are  taken  from  that  publication,  and  need  no  further 
comment  or  explanation. 

"  From  the  following  table  the  bacterial  population  of  414  flies  is 
pretty  well  represented.  The  domestic  fly  is  passing  from  a  disgusting 
nuisance  and  troublesome  pest  to  a  reputation  of  being  a  dangerous 
enemy  to  human  health,  .  .  .  The  numbers  of  bacteria  on  a  single  fly 
may  range  all  the  way  from  550  to  6,600,000.  Early  in  the  fly  season  the 
numbers  of  bacteria  on  flies  are  comparatively  very  small,  while  later  the 
numbers  are  comparatively  very  large.  The  place  where  flies  live  also 
determines  largely  the  number  that  they  carry.  The  average  for  ^14- 
flies  2vas  about  one  and  one  fourth  million  bacteria  on  each.  It  hardly 
seems  possible  for  so  small  a  bit  of  life  to  carry  so  large  a  number  of 
organisms.  .  .  .  The  objectionable  class  coliaerogenes  type  was  two 
and  one  half  times  as  abundant  as  the  favorable  acid  type." 

From  the  experiments  previously  cited  it  may  be  seen  that  the  fly 
becomes  infected  by  walking  over  infective  materials,  both  its  feet  and 
wings  becoming  contaminated.  The  intestinal  contents  of  flies  become 
infected  by  feeding  on  infective  material,  and  bacteria  are  dejected  in 
the  fly  "  specks."  It  furthermore  seems  plausible  that  flies  might  be- 
come infected  in  the  larval  stage  by  developing  in  fecal  matter  and  that 
the  newly  emerged  flies  would  already  be  dangerous.  Under  experi- 
mental conditions  Graham-Smith  ^  has  produced  infected  blowflies 
by  feeding  the  larvae  on  meat  infected  with  spores  of  Bacillus  anthracis. 
He  found  that  the  blowflies  remained  heavily  infected  for  at  least 
two  days  after  emerging  and  that  the  bacillus  could  be  cultivated  either 
from  the  limbs  or  intestinal  contents  of  the  flies  more  than  fifteen  or 
nineteen  days  old. 

Human  foods  are  infected  by  flies  primarily  by  direct  contact  through 
the  touch  of  feet,  proboscides  and  wings ;  and  secondly,  through  fly 
*'  specks  "  (feces) ;  and  finally,  files  grossly  infect  liquids  by  accidentally 
dropping  into  the  fluid,  —  this  is  especially  true  of  milk. 

The  opportunity  for  flies  to  become  infected  is  so  great  in  all  com- 
munities, even  the  most  sanitary,  that  no  fly  should  be  trusted  to  alight 
on  food  prepared  for  human  consumption.     The  following  quotation 

1  Esten  and  Mason,  1908.  Sources  of  Bacteria  in  Milk.  Storrs  Agric.  Exp. 
Sta.,  Bull.  No.  51. 

2  Graham-Smith,  G.  S.,  1911.  Further  observations  on  the  ways  in  which 
artificially  infected  flies  carry  and  distribute  pathogenic  and  other  bacteria. 
Reports  of  the  local  Government  Board  on  Public  Health  and  Medical  Subjects. 
(New  Series  No.  53.)     Further  Reports  No.  4,  pp.  31-48. 


176       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


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THE   COMMON  HOUSE   FLY  177 

from  Nuttall/  whose  careful  judgment  is  here  considered,  is  directly 
to  the  point,  viz. :  "  It  should  be  remembered  that  a  fly  may  cause  rela- 
tively gross  infection  of  any  food  upon  which  it  alights  after  having  fed 
upon  infective  substances,  be  they  typhoid,  cholera  or  diarrhea  stools. 
Not  only  is  its  exterior  contaminated,  but  its  intestine  is  charged  with 
infective  material  in  concentrated  form  which  may  be  discharged  un- 
digested upon  fresh  food  which  it  seeks.  Consequently,  the  excrement 
voided  by  a  single  fly  many  contain  a  greater  quantity  of  the  infective 
agents  than,  for  instance,  a  sample  of  infected  water.  In  potential 
possibilities  the  droppings  of  one  fly  may,  in  certain  circumstances,  weigh 
in  the  balance  as  against  buckets  of  water  or  of  milk !  " 

That  flies  may  serve  as  carriers  of  disease  has  long  been  suspected, 
e.g. :  "Mercurialis  (1577)  considered  that  they  carried  the  virus  of  plague 
from  those  ill  or  dead  of  plague  to  the  food  of  the  healthy.  Sydenham 
(1666)  remarked  that  if  swarms  of  insects,  especially  house  flies,  were 
abundant  in  summer,  the  succeeding  autumn  was  unhealthy.  A  number 
of  authors,  e.g. :  Crawford  (1808),  might  be  cited  who  refer  in  a  general 
way  to  insects,  especially  house  flies,  as  carriers  of  infection ;  Moore 
(1853)  refers  to  flies  as  possible  carriers  of  cholera,  typhoid,  tuberculosis, 
anthrax  and  leprosy;  Leidy  (1872)  refers  to  flies  as  carriers  of  the  in- 
fection of  hospital  gangrene  and  of  wound  infection  "  (quotation  from 
Nuttall,  1909,  loc.  cit). 

Typhoid  Fever.  —  The  causative  organism  {Bacillus  typhosus)  of 
typhoid  fever  belongs  to  the  typhoid-dysentery  group,  and  is  found 
outside  the  human  body  "  only  in  those  situations  where  it  could  be 
more  or  less  directly  traced  to  an  origin  in  the  discharge  of  a  typhoid 
patient  or  convalescent."  Jordan  ^  and  others  have  shown  that  the 
life  of  this  germ  in  the  water  of  flowing  streams  is  of  comparatively 
short  duration,  and  that  multiplication  does  not  ordinarily  take  place 
in  water;  indeed,  a  steady  decline  in  numbers  goes  on.  Infection 
caused  by  transmission  through  the  air  is  exceedingly  rare  according 
to  these  authors,  but  soil  on  the  contrary  may  become  contaminated 
through  buried  human  excrement,  or  otherwise,  and  continue  to  be  a 
source  of  infection  for  a  much  longer  time  than  water.  Notwithstanding 
these  facts,  the  majority  of  typhoid  fever  epidemics  are  traceable  to  water 
infection,  but  indicate  fresh  contamination  and  not  one  of  long  standing. 

Within  the  human  body  the  typhoid  bacilli  are  found  mainly  in  the 
intestine,  also  in  the  urinary  bladder,  and  in  the  majority  of  cases  in  the 
blood  stream.  The  bacilli  are  discharged  from  the  body  with  the  feces 
and  the  urine ;  and  are  often  present  in  such  discharges  for  a  period  of 
ten  weeks,  and  in  chronic  carriers  for  years  after  recovery.     An  added 

1  Nuttall,  G.  H.  F.,  and  Jepson,  F.  P.,  1909.  The  part  played  by  Musca 
doviestica  and  allied  (non-biting)  flies  in  the  spread  of  infective  diseases.  Re- 
ports to  the  local  Government  Board  of  Public  Health  and  Medical  Subjects. 
(New  Series  No.  16.)     London. 

2  Jordan,  Edwin  O.,  1908.  A  Textbook  of  General  Bacteriology.  W.  B. 
Saunders  &  Co.     Philadelphia,  pp.  557. 


178      _MEDICAL  AND   VETERINARY  ENTOMOLOGY 

source  of  danger  is  the  presence  of  virulent  bacilli  in  very  light  cases 
of  typhoid  fever,  known  as  "  walking  typhoid,"  where  little  or  no  pre- 
caution is  exercised. 

The  above  facts  aid  in  interpreting  the  role  of  flies  in  typhoid  trans- 
mission. Flies  are  attracted  by  excrementous  matter,  as  has  already 
been  stated,  and  thus  contaminate  their  mouth  parts  and  feet,  which, 
if  the  feces  contain  virulent  bacilli,  must  now  fairly  reek  with  filth  and 
disease.  Thus  equipped  the  fly  next  makes  its  way  to  the  dining 
room,  grocery  store,  fruit  stand,  etc.,  depositing  there  on  the  human 
food  the  infective  dejecta  by  means  of  its  soiled  proboscis  and  feet. 
Thus,  during  the  Spanish  American  war,  flies  with  lime-covered  feet 
were  actually  seen  crawling  over  the  food  of  the  soldiers.  The  whit- 
ened feet  were  the  result  of  lime  and  filth  collected  from  the  camp 
latrines.  The  depredations  of  typhoid  fever  at  that  time  really  mark 
the  beginning  of  the  widespread  campaign  against  the  house  fly. 

Jordan  ^  states  "  not  only  may  bacilli  stick  to  the  legs  and  wrings 
of  these  insects,  but  if  swallowed  they  may  survive  the  passage  of  the 
alimentary  tract.  Typhoid  bacilli  have  been  isolated  from  house  flies 
captured  in  houses  in  Chicago,  in  the  neighborhood  of  badly  kept  privy 
vaults  used  by  typhoid  patients,  and  it  has  been  shown  experimentally 
that  living  bacilli  may  remain  in  or  upon  the  body  of  flies  for  as  long  as 
twenty- three  days  after  infection." 

The  writer's  attention  was  at  one  time  called  to  a  series  of  sporadic 
cases  of  typhoid  fever,  plausibly  traceable  to  flies,  thus :  a  certain  car- 
penter recently  recovered  from  typhoid  fever,  resumed  his  work,  making 
use  of  a  box  privy,  such  as  is  often  used  in  connection  with  buildings 
under  construction.  In  the  immediate  vicinity  there  lived  a  milk  dealer, 
who,  after  washing  his  cans,  placed  them  on  the  roof  of  a  shed  to  drain. 
Flies  are  fond  of  milk,  even  highly  diluted  with  water.  The  cases  of 
typhoid  fever  in  question  were,  on  investigation,  found  to  be  cus- 
tomers of  this  particular  dealer.  The  argument  is  good  and  reasonably 
conclusive. 

The  pollution  of  the  waters  of  New  York  harbor  has  been  made  the 
subject  of  special  study  by  Jackson.^  In  his  report  to  the  "Merchants' 
Association  "  of  New  York  he  shows  that  the  sewage  is  not  carried  away 
by  the  tides,  and  "  that  at  many  points  sewer  outfalls  have  not  been 
carried  below  the  low-water  mark,  in  consequence  of  which  the  solid 
matter  from  the  sewers  has  been  exposed  on  the  shores."  These  deposits 
were  found  to  be  covered  with  flies,  thus  affording  ample  opportunity 
for  the  transmission  of  typhoid.  It  was,  furthermore,  found  that  the 
greater  number  of  typhoid  cases  were  found  near  the  water  front,  and  if 

1  Jordan,  Edwin  O.,  1908  (loc.  cit.). 

2  Jackson,  Daniel  D.,  1908.  Pollution  of  New  York  harbor  as  a  menace 
to  health  by  the  dissemination  of  intestinal  diseases  through  the  agency  of  the 
common  house  fly.  Report  to  the  Water  Pollution  Committee  of  New  York 
City. 


THE   COMMON  HOUSE   FLY  179 

the  curve  showing  the  prevalence  of  cases  was  set  back  to  accord  with 
the  average  time  of  infection,  it  coincided  with  the  curve  showing  the 
prevalence  of  house  fiies.  The  fly  curve,  of  course,  also  coincides  with 
the  temperature  curve,  but  hot  weather  cannot  account  for  the  dis- 
semination of  the  typhoid  bacillus,  nor  for  its  presence. 

Various  authors  at  sundry  times  have  shown  experimentally  that 
Musca  domestica  can  carry  Bacillus  tyijhosus  after  having  fed  on  con- 
taminated material,  both  by  contact  with  feet,  proboscis  and  wings 
(Firth  and  Horrocks)  ^  and  via  the  digestive  tract  (Faichnie). 

Flies  captured  in  houses  occupied  by  typhoid  fever  cases  have  also 
been  shown  to  be  infected ;  thus  Hamilton  found  B.  typhosus  in  five 
out  of  eighteen  flies  captured  under  the  above  condition  in  Chicago, 
and  Ficker  -  made  observations  in  Leipzig  with  similar  results. 

Thus  the  case  against  the  house  fly  as  a  carrier  of  typhoid  is  conclu- 
sive. 

Dysentery.  —  There  are  at  least  two  varieties  of  dysentery ;  of  which 
one  is  caused  by  a  bacillar  organism,  as  in  typhoid  fever,  and  is  known 
as  Bacillus  dysenterioe,  and  the  other  variety  is  caused  by  a  protozoan 
organism  (Entamoeba)  known  as  Entamoeba  histolytica.  The  former 
variety  is  known  to  be  the  prevalent  type  in  temperate  climates,  while 
the  latter  is  common  in  the  tropics.  The  causative  organism  of  both 
is  found  in  great  numbers  in  the  stools  of  patients.  The  mode  of 
infection  is  much  the  same  as  in  typhoid  fever. 

Summer  Diarrhea  in  Infants.  —  A  type  of  Bacillus  dysentericB  is 
present  in  the  stools  of  infants  suffering  from  summer  complaint. 
Thousands  of  infants  die  every  summer  from  this  disease.  Howard  ^ 
states  that  in  1908  the  number  of  deaths  due  to  summer  complaint  was 
52,213,  of  which  44,521  were  under  two  years.  It  is  thus  in  the  helpless 
months  of  the  child's  life  that  this  disease  is  most  dangerous.  At  this 
age  the  infants  are  greatly  molested  by  flies  (when  these  are  present) 
attracted  by  milk  vomits  and  especially  stools,  which  often  remain 
exposed  for  a  long  time  and  to  which  flies  have  free  access.  From 
these  stools  the  flies  travel  to  the  child's  face  and  mouth  where  they 
linger  menacingly.  Mothers  who  fail  to  protect  their  babies  against 
the  disease-bearing  house  fly  are  criminally  exposing  these  innocents  to 
deadly  disease.  Keep  the  baby  well  protected  by  screens,  and  if  by 
accident  a  fly  has  fallen  into  the  milk,  it  is  better  to  throw  it  away. 
Furthermore,  milk  receptacles  can  easily  be  kept  covered,  and  the  fly  in 
the  milk  is  usually  a  sign  of  carelessness.  Carefully  protect  nipples  and 
nursing  bottles  against  flies. 

1  See  NuttaU,  G.  H.  F.,  and  Jepson,  F.  P.,  1909.  The  part  played  by 
Musca  doviestica  and  allied  (non-biting)  flies  in  the  spread  of  infective  diseases. 
Reports  to  the  Local  Government  Board  on  Public  Health  and  Medical  Sub- 
jects.    New  Series  16,  No.  4,  pp.  13-41. 

*  Nuttall  and  Jepson,  1909  {loc.  cit.). 

'  Howard,  L.  O.,  1911.  The  house  fly,  disease  carrier.  F.  A.  Stokes  Co. 
New  York,  pp.  xix  +  312. 


180       MEDICAL  AND   VETERINARY   ENTOMOLOGY 

Nuttall  in  summing  up  the  evidence  against  the  house  fly  makes  the 
following  statement,  "  All  authorities  agree  that  flies  rest  under  strong 
suspicion  of  serving  as  disseminators  of  diarrheal  infection." 

Tuberculosis.  —  Tuberculosis  is  caused  by  a  specific  organism, 
Bacillus  tuberculosis,  which  may  invade  practically  every  organ  and 
tissue  of  the  human  body.  The  lungs  are  commonly  the  seat  of  lesions, 
as  are  the  intestines,  the  liver  and  the  urogenital  organs.  The  causa- 
tive germs  find  their  way  outside  the  body  in  the  sputum,  the  feces 
and  the  urine,  depending  on  the  location  of  the  lesions. 

In  the  study  of  transmission  the  considerable  power  of  resistance, 
which  these  bacilli  possess  is  highly  important.  Dried  phthisical 
sputum  has  been  found  to  contain  virulent  bacilli  after  two  months. 
Sputum  has  been  found  to  contain  living  tubercle  bacilli  even  after 
being  allowed  to  putrefy  for  several  weeks.  The  germicidal  power 
of  sunlight  is  very  great,  but  according  to  Jordan  ^  it  requires  from 
twenty  to  twenty-four  hours'  exposure  to  sunlight  or  even  longer  to 
kill  the  tubercle  bacillus  when  present  in  sputum. 

These  facts  are  most  important  when,  coupled  with  them,  it  is  rec- 
ognized that  infection  is  commonly  accomplished  by  way  of  the  in- 
testinal tract,  with  infected  food  introduced  into  the  mouth.  "  Von 
Behring  maintains  that  the  vast  majority  of  all  cases  of  lung  tuber- 
culosis are  of  intestinal  origin,  and  there  is  no  doubt  that  pulmonary 
tuberculosis  can  originate  from  swallowing  tubercle  bacilli  "  (Jordan). 

It  has  been  proved  beyond  doubt  that  the  house  fly  can  carry  with 
it  in  its  intestinal  tract  the  Bacillus  tuberculosis.  "  The  belief  that 
flies  {Musca  domestica)  which  have  fed  on  tubercular  sputum  may 
serve  as  carriers  and  disseminators  of  the  tubercle  bacillus  first  led 
Spillmann  and  Haushalter  (1887)  to  investigate  the  problem.  They 
examined  such  flies  and  also  their  excreta  deposited  on  the  walls  and 
windows  of  a  hospital  ward,  and  were  able  to  determine  microscopically 
the  presence  of  large  numbers  of  tubercle  bacilli,  both  in  the  intestines 
of  the  flies  and  their  excrement  "  (Nuttall).  Howard  quotes  the  follow- 
ing from  a  "  paper  by  Dr.  Frederick  T.  Lord  (1904)  of  Boston  "  : 

"  1 .  Flies  may  ingest  tubercular  sputum  and  excrete  tubercle  baciUi,  the  virulence 
of  which  may  last  for  at  least  fifteen  days. 

"  2.   The  danger  of  human  infection  from  tubercular  flyspecks  is  by  the  injection 
of  the  specks  on  the  food.     Spontaneous  liberation  of  tubercle  bacUh 
from  flyspecks  is  unlikely.     If  mechanically  disturbed,  infection  of  the 
surrounding  air  may  occur. 
"  As  a  corollary  to  these  conclusions  it  is  suggested  that  — 

"  3.  Tubercular  material  (sputum,  pus  from  dischargmg  sinuses,  fecal  matter 
from  patients  with  intestinal  tuberculosis,  etc.)  should  be  carefully  pro- 
tected from  flies,  lest  they  act  as  disseminators  of  the  tubercle  bacUli. 

"4.  During  the  fly  season  greater  attention  should  be  paid  to  the  screening  of 
rooms  and  hospital  wards  containing  patients  with  tuberculosis,  and 
laboratories  where  tubercular  material  is  examined. 

1  Jordan,  Edwin  O.,  1908  {loc.  cit.). 


THE   COMMON  HOUSE   FLY  181 

"  5.  As  these  jirecautions  \voul(l  not  eliminate  fly  infection  by  patients  at  large, 
foodstuffs  should  be  protected  from  the  flies  which  may  already  have  in- 
gested tuljercular  material." 

The  investigations  by  Dr.  Ch.  Andre  of  the  University  of  Lyons  were 
reported  at  the  Anti-Tuberculosis  Congress  at  Washington,  1908,  viz, : 

"Flies  are  active  agents  in  the  dissemination  of  Koch's  bacillus  because  they 
are  constantly  going  hack  and  forth  between  contagious  sputa  and  feces,  and 
foodstuffs,  especially  meat,  fruit,  milk,  etc.,  which  they  pollute  by  contact  with 
their  feet,  and  especially  with  their  excretions. 

"  The  experimental  researches  of  the  author  show  the  following: 

"1.  Flies  caught  in  the  open  air  do  not  contain  any  acid-fast  bacilli  that  could 
be  mistaken  for  the  baciUus  of  Koch. 

"2.  Flies  that  have  been  fed  on  sputum  evacuate  considerable  quantities  of 
bacilli  in  their  excretions.  The  baciUi  appear  six  hours  after  ingestion  of  the 
sputum,  and  some  may  be  found  as  long  as  five  days  later.  These  flies,  there- 
fore, have  plenty  of  time  to  carry  these  bacilli  to  a  great  distance,  and  to  con- 
taminate food  in  houses  apparently  protected  from  contagion,  because  not  in- 
habited by  a  consumptive. 

"3.  Food  polluted  by  flies  that  have  fed  on  sputa  contains  uifective  bacilli 
and  produces  tuberculosis  in  the  guinea  pigs. 

"4.  Flies  readily  absorb  bacilli  contained  in  dry  dust. 

"5.  Flies  caught  at  random  in  a  hospital  ward  produced  tuberculosis  in  the 
guinea  pig. 

"Practical  conclusions.  —  The  sputa  and  feces  of  tuberculosis  subjects  must 
be  disinfected ;  flies  should  be  destroyed  as  completely  as  possible ;  foodstuffs 
should  be  protected  by  means  of  covers  made  of  wire  gauze." 

"  ^  .'^    .       .  . 

Asiatic  Cholera.  —  Asiatic  cholera,  as  the  name  implies,  is  endemic 

in  Asia  (India),  but  has  spread  over  the  larger  part  of  the  world  during 

the    past  century,   becoming   endemic    in  Africa   and   Europe.      The 

disease  relates  to  the  intestinal  tract,  and  is  of  bacterial  origin  (Spirillum 

choleras).     The  cholera  spirillum  leaves  the  body  with  the  stools,  and 

infection  is  traceable  to  this  source.     "  Upon  the  surface  of  vegetables 

and  fruits  kept  in  a  cool  moist  place,  experiments  have  shown  that  the 

spirillum  may  retain  its  vitality  for  from  four  to  seven  days  "  (Jordan). 

Cholera  was  among  the  first  diseases  with  which  the  house  fly  was 
associated  as  a  carrier,  and  the  experimental  evidence  is  truly  convincing. 
Tizzoni  and  Cattini  in  Bologna  in  1886  isolated  cholera  vibrios  from 
flies  caught  in  cholera  wards.  Simmonds  in  1892  captured  flies  in  the 
post-mortem  morgue  in  Hamburg  and  isolated  cholera  vibrios  from  these 
in  large  numbers. 

There  remains  no  doubt  that  flies  are  important  carriers  of  cholera, 
and  that  bodies  dead  of  cholera,  stools  and  vomits  of  patients,  should 
be  protected  from  flies,  and  that  foods  should  be  most  carefully  screened. 

Framboesia  (tropical  ulcer  or  yaws)  is  caused  by  SpirochcFta 
pertenuis.  The  disease  is  w'idely  distributed  in  the  tropics.  The 
spirochsetes  are  found  in  the  superficial  ulcers  on  the  hands,  face,  feet 
and  other  parts  of  the  body.     The  following  quotation  from  Nuttall 


182       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

and  Jepson  ^  is  convincing  enough  that  Miisca  domestica  is  amply 
able  to  transmit  this  disease :  "  Castellani  (1907)  tested  the  matter 
of  the  fly  transmission  of  yaws  by  experimental  methods.  He  allowed 
M.  domestica  to  feed  (1)  upon  yaws  material  (scraping  from  slightly 
ulcerated  papules),  and  (2)  upon  semiulcerated  papules  on  the  skin  of 
these  yaws  patients.  In  both  cases  he  was  able  to  discover  the  SpirochcBta 
pertenuis  in  microscopic  preparations  made  from  the  flies'  mouth  parts 
and  legs.  Furthermore,  he  allowed  M.  domestica  to  feed  on  yaws  mate- 
rial (1  and  2  as  above)  and  afterwards  transferred  them  to  scarified  areas 
upon  the  eyebrows  of  monkeys.  Of  15  monkeys  thus  experimented 
upon  three  developed  yaws  papules  at  the  places  which  had  been  con- 
taminated by  the  flies." 

Ophthalmia.  —  In  commenting  on  ophthalmia  as  carried  by  flies 
Howard  ^  has  the  following  to  say :  "  Dr.  Lucien  Howe  of  Buffalo 
informed  the  writer  (Howard)  that  in  his  opinion  the  ophthalmia  of  the 
Egyptians  is  also  transferred  by  flies  and  presumably  by  the  house  fly, 
and  referred  the  writer  (Howard)  to  a  paper  which  he  read  before  the 
Seventh  International  Congress  of  Ophthalmology  at  Wiesbaden  in  1888. 
He  referred  to  the  extraordinary  prevalence  of  purulent  ophthalmia 
among  the  natives  up  and  down  the  river  Nile  and  to  the  extraordinary 
abundance  of  the  flies  in  that  country.  He  spoke  of  the  dirty  habits 
of  the  natives  and  their  remarkable  indifference  to  the  visits  of  flies, 
not  only  children,  but  adults,  allowing  flies  to  settle  in  swarms  about 
their  eyes,  sucking  the  secretions,  and  never  making  any  attempt  to 
drive  them  away.  Doctor  Howe  called  attention  to  the  fact  that 
the  number  of  cases  of  this  eye  disease  always  increases  when  the  flies 
are  present  in  the  greatest  numbers  and  the  eye  trouble  is  most  prev- 
alent in  the  place  where  the  flies  are  most  numerous.  In  the  desert, 
where  flies  are  absent,  eyes  as  a  rule  are  unaft'ected.  He  made  an  ex- 
amination of  the  flies  captured  upon  diseased  eyes  and  found  on  their 
feet  bacteria  which  were  similar  to  those  found  in  the  conjunctival 
secretions.  Flies  captured  in  Egypt  swarming  about  the  eyes  of 
ophthalmia  patients  and  sent  to  Washington,  D.C.,  were  identified  as 
Musca  domestica." 

Other  Diseases  Carried  by  the  House  Fly.  —  Under  certain  favorable 
conditions  it  is  also  quite  probable  that  the  fly  may  be  a  carrier  of 
anthrax,  plague,  gonorrheal  infection,  and  possibly  smallpox. 

Eggs  of  Parasitic  Worms.  —  The  most  extensive  and  careful  work 
on  the  dispersal  of  eggs  of  parasitic  worms  by  the  house  fly  has  been 
done  by  Nicoll  ^  and  the  following  is  a  summary  of  his  investigations 
in  that  respect.     Flies  feed  readily  upon  infective  material  such  as 

^  Nuttall  and  Jepson,  1909  {loc.  cil.). 

2  Howard,  L.  0.,  1911  {loc.  cit.). 

3  Nicoll,  William  (1911).  "On  the  part  played  by  Flies  in  the  Dispersal 
of  the  Eggs  of  Parasitic  Worms."  Reports  to  the  Local  Government  Board  on 
Public  Health  and  Medical  Subjects  (New  Series,  No.  53).  Further  Reports 
(No.  4)  on  Flies  as  Carriers  of  Infection.     London. 


THE   COMMON  HOUSE   FLY  183 

excrement  laden  with  eggs  from  parasitic  worms  and  even  upon  evac- 
uated worms.  Eggs  may  be  conveyed  by  flies  from  excrement  to  food 
in  two  ways,  namely  on  the  external  surface  of  their  body  and  in  their 
intestines.  The  latter  mode  is  practicable  only  when  the  diameter  of 
the  eggs  is  under  .05  mm.  Eggs  with  a  diameter  of  up  to  .09  mm.  may 
be  conveyed  on  the  external  surface ;  however,  these  adhering  eggs  are 
usually  gotten  rid  of  by  the  fly  wdthin  a  short  time,  while  those  harbored 
in  the  intestine  may  remain  there  for  two  days  or  longer. 

The  eggs  may  remain  alive  and  subsequently  cause  infection  in 
either  of  these  ways ;  however,  this  depends  on  their  resisting  powers. 
It  was  found  that  material  containing  eggs  of  parasites,  and  in  particular 
ripe  segments  of  tapeworms,  remain  a  source  of  infection  through  flies 
as  long  as  two  weeks. 

The  eggs  of  the  following  parasitic  worms  were  shown  experimen- 
tally to  be  capable  of  transmission  by  Musca  domestica:  Tconia 
solium,  Tconia  serrata,  Tcenia  marginata,  Hymenolepis  nana,  Dipy- 
lidium  caninum,  Dibothriocephalus  latus  (?),  Oxyuris  vermicularis,  Tri- 
churis  (Trichocephalus)  trichiurus,  both  internally  and  externally, 
Necator  americanus,  Arikylostoma  caninum,  Sclerostomum  equinum, 
Ascaris  megalocephala,  Toxascaris  limbata  {Ascaris  canis  e.  p.), 
Hymenolepis  diminuta  externally  only.  No  trematode  parasites 
were  experimented  with  and  the  observations  of  Stiles  that  the  larval 
fly  can  ingest  Ascarid  eggs  and  pass  them  on  to  the  adult  fly  was  not 
confirmed. 


CHAPTER  XIV 
HOUSE  FLY  CONTROL 

Introduction.  —  Agitation  for  the  extirpation  of  any  given  species 
always  brings  with  it  a  wave  of  protest  based  mainly  on  the  idea  that 
there  is  a  balance  in  nature  which  should  not  be  disturbed.  The  wise 
agitator  calls  for  control  rather  than  elimination,  not  merely  to  appease 
the  wrath  of  opponents,  but  because  control  is  possible,  while  elimination 
of  any  given  species  is  practically  impossible  except  for  some  species  in 
given  isolated  regions.  A  cosmopolitan  species  of  such  abundance  and 
extensive  breeding  habits  as  Musca  domestica  is  an  object  for  control 
rather  than  one  for  elimination. 

The  house  fly  is  regarded  by  many  as  necessary  in  Nature's  economy, 
that  it  is  most  abundant  where  most  needed.  It  is  time  and  again 
asserted  that  the  house  fly,  though  admittedly  a  disease  carrier,  must 
be  good  for  something,  otherwise  it  would  not  be  in  existence,  and 
should  therefore  not  be  molested.  The  following  is  an  extract  from  a 
letter  received  by  the  writer,  which  illustrates  well  the  objections  fre- 
quently raised : 

i^^  "Dear  Sir:  I  enclose  a  slip  that  I  cut  from  a  paper  saying  that  you  are 
down  on  the  poor  flies.  Now,  I  would  like  to  take  their  part.  I  have  known 
them  nigh  on  to  thirty  years,  and  I  never  knew  of  a  sickness  that  could  be  laid 
to  them.  I  know  they  make  a  lot  of  dirt,  spoU  picture  frames  and  such,  tickle 
your  nose  in  the  morning  if  you  don't  get  up,  but  they  make  a  nice  food  for 
young  poultry.  .  .  .  Only  a  few  years  back  they  were  considered  a  blessing, 
as  they  eat  stuff  that  would  make  harm  .  .  .  they  spot  thmgs,  make  a  lot  of 
cleaning,  that  keeps  folks  out  of  mischief.  If  mosquitoes  or  flies  harm  anyone, 
it's  because  the  blood  is  out  of  order,  and  they  had  better  look  to  it  and  mend 
their  ways.  ...  I  think  if  you  would  get  after  them  of  your  size,  such  as  .  .  . 
and  .  .  .,  they  are  parasites  that  do  more  harm  than  insects  and  reptiles  com- 
bined ...  so  if  you  want  to  scrap  go  after  them  .  .  .  this  torturing  poor 
helpless  creatures  to  find  ways  to  prolong  lives  that  are  worthless  ...  we 
must  all  die  some  way  .  .  .  hoping  you  will  let  the  flies  and  little  things 
alone.  ..." 

In  reply  to  the  above  rather  trivial  objections  it  may  be  said  in  the 
first  place  that  the  house  fly  is  by  no  means  a  good  scavenger ;  on  the 
contrary  its  function  in  that  regard  is  very  poor,  since  the  material  in 
which  it  breeds  is  not  greatly  reduced,  and  secondly  there  is  no  good 
excuse  for  the  collection  and  prolonged  exposure  of  fecal  material  and 
decaying  kitchen  refuse  in  which  the  fly  breeds.     Simply  on  the  basis 

184 


HOUSE   FLY  CONTROL  185 

of  human  decency  such  refuse  should  not  be  permitted  to  collect  and 
remain  exposed  long  enough  to  breed  flies.  Domesticated  animals  are 
necessary  to  our  present  state  of  civilization,  but  our  methods  of  stable 
sanitation  and  manure  disposal  are  far  behind  the  times,  all  but 
barbaric. 

As  innocent  as  flies  may  appear,  they  rank  nevertheless  among  the 
most  dangerous  enemies  of  man.  There  is  no  virtue  in  the  house  fly, 
and  there  is  no  reason  why  it  should  continue  to  swarm  in  hordes  in 
any  civilized  community.  It  is  a  poor  advertisement  for  civilization. 
Dr.  E.  P.  Felt  ^  has  so  well  said  "  our  descendants  of  another  century 
will  stand  in  amazement  at  our  blind  tolerance  of  such  a  menace  to 
life  and  happiness." 

The  house  fly  can  be  controlled  without  question.  This  is  demon- 
strated by  the  scarcity  of  flies  in  localities  where  cleanliness  about 
stables  and  houses  prevails  throughout  a  number  of  adjacent  city  blocks. 
The  work  of  control  can  be  greatly  furthered  by  the  individual  citizen, 
but  as  is  so  well  stated  by  the  California  State  Board  of  Health  in  Bulletin 
No.  11  (1909),  "  This  work  can  be  done  only  by  a  united  efi^ort.  The 
citizen  must  do  the  work,  and  should  do  it  willingly,  but,  if  negligent, 
the  strong  hand  of  the  law  should  compel  it."  The  citizen  must,  how- 
ever, have  instruction  in  the  matter,  because  there  is  the  greatest  ig- 
norance relative  to  the  life  history  and  development  of  the  housefly 
and  disease-transmitting  insects  in  general.  The  writer  finds  that  this 
ignorance  is  as  prevalent  among  the  educated  as  among  the  uneducated. 

The  main  facts  pertaining  to  development  and  habits  indicate  the 
most  desirable  control  measures  to  be  pursued.  If  95  per  cent  of  our 
house  flies  develop  in  horse  manure,  —  and  this  is  true  under  ordinary 
conditions,  —  the  point  of  attack  is  clearly  outlined. 

Sanitary  Stable  Construction.  —  Since  the  principal  breeding  places 
of  the  house  fly  are  found  in  and  about  stables,  particular  attention 
must  be  paid  such  situations  with  special  reference  to  the  disposal  of 
manures  and  urine.  In  the  first  place  the  stable  should  have  a  concrete 
floor.  A  very  practical  consideration  of  this  subject  is  to  be  found  in 
Bulletin  No.  97,  North  Dakota  Agricultural  Experiment  Station,  from 
which  the  following  suggestions  are  largely  taken.  Although  higher 
than  wood  in  first  cost,  cement  concrete  meets  the  requirements  of  a 
good  floor  better  than  any  other  available  material.  Concrete  floors, 
according  to  the  bulletin  mentioned,  are  considered  best  for  several 
reasons.  "1.  They  are  economical  because  they  are  durable.  Wooden 
floors  last  from  three  to  five  years  with  a  maximum  of  about  ten  years, 
if  of  the  best  construction,  while  the  durability  of  good  concrete  floors 
equals  that  of  the  building.  2.  They  save  labor  because  of  their  even- 
ness, which  permits  of  thorough  and  easy  cleaning.  3.  They  are  sani- 
tary not  only  because  they  can  be  kept  clean,  but  because  they  are 

1  Felt,  E.  P.,  1909.     Control  of  household  insects.     N.  Y.  State  Museum 
BuU.  No.  129,  pp.  5^7. 


186        MEDICAL  AND  VETERINARY  ENTOMOLOGY 

easily  drained  and  are  water-tight  enough  to  exclude  ground  water  and 
prevent  the  liquid  manure  from  leaching  into  and  polluting  the  soil. 

"  The  chief  objection  to  concrete  floors  are  that  they  are  cold  and 
slippery.  To  the  first  may  be  replied  that  in  reality  concrete  is  no 
colder  than  wood  subjected  to  the  same  temperature  but  on  account  of 
being  a  better  conductor  of  heat  concrete  carries  away  the  bodily  heat 
of  the  animals  faster  if  they  come  in  direct  contact  with  it.  This  is  not  a 
serious  objection,  for  even  wood  is  too  cold  for  animals  to  lie  on  without 
bedding,  which  should  be  supplied  liberally  on  any  floor.  Straw  is  a 
poor  conductor  of  heat  and  if  a  sufficient  amount  of  bedding  is  used,  the 
bodily  heat  of  the  animals  will  be  retained  as  well  on  concrete  as  on  wood, 
which  is  apt  to  be  more  or  less  wet  or  soggy.  A  generous  use  of  bedding 
is  desirable  not  only  because  it  adds  to  the  comfort  of  the  animals,  but 
because  of  the  increased  amount  of  manure  which  in  turn  means  in- 
creased fertility  of  the  farm.  The  objection  of  slipperiness  may  be 
overcome  by  making  the  wearing  surface  scored  or  grooved  into  blocks 
before  it  has  hardened.  These  sections  made  from  4  to  6  inches  square 
furnish  a  good  foothold  for  the  animals  and  make  a  very  neat  appear- 
ance. 

"  The  floor  should  be  raised  about  one  foot  above  the  surface  of  the 
ground  to  insure  drainage.  If  earth  has  been  filled  in  to  secure  this 
elevation,  it  must  be  thoroughly  compacted  so  as  to  prevent  uneven 
settling  and  subsequent  cracking  of  the  floor.  It  is  a  good  practice 
to  make  the  desired  fill  as  soon  as  the  foundation  is  completed  because 
it  can  be  done  more  conveniently  at  that  time  and  the  fill  will  have 
proper  time  to  settle  before  the  floor  is  put  on. 

"  Concrete  stable  floors  should  be  about  5  inches  thick.  The  lower 
4  inches  should  be  made  of  concrete  in  the  proportion  of  one  part  cement, 
2\  parts  clean,  coarse  sand  and  five  parts  screened  gravel  or  broken  stone 
and  finished  before  the  concrete  has  set,  with  a  one-inch  mortar  of  one 
part  Portland  cement  to  two  parts  clean  and  coarse,  but  sharp  sand. 
If  the  sand  or  cement  are  not  first-class,  this  proportion  had  best  be 
changed,  for  horse  barns  at  least,  to  one  part  cement  to  1^  parts  sand. 

"  Before  laying  the  concrete  a  foundation  of  porous  material,  such  as 
cinders  or  gravel,  should  be  spread  evenly  on  the  surface  and  thoroughly 
tamped  down.  The  depth  of  this  foundation  will  depend  upon  the 
drainage  of  the  soil  but  where  a  fill  of  one  foot  of  earth  has  been  pro- 
vided, as  previously  described,  this  foundation  need  not  be  more  than 
four  inches  thick." 

In  constructing  a  concrete  floor  provision  must  be  made  to  carry 
away  the  urine  from  the  animals  and  water  used  in  cleansing  the  floors 
and  stalls.  Suggestions  from  the  above-named  bulletin  are  here  again 
useful,  namely,  the  stall  floors  should  be  given  a  1  inch  drop  from  the 
manger  to  the  manure  gutter,  which  latter  should  be  "  6  inches  deep 
and  14  inches  wide.  In  order  to  facilitate  the  draining  away  of  the 
liquids  a  3-inch   U-shaped  channel  is  sometimes  made  in  the  bottom 


HOUSE   FLY   CONTROL  187 

of  the  gutter  next  to  the  manure  alley,  but  this  is  not  necessary  where  a 
slope  is  given  the  gutter  bottom.  The  gutter  should  be  given  a  uniform 
fall  of  3  inches  to  100  feet  and  the  floor  of  the  manure  alley  should  have 
a  slope  towards  the  gutter  of  1  inch  to  10  feet.  A  small  water-tight 
liquid  manure  cistern  may  be  provided  outside  the  barn  into  which  the 
gutter  drains,  but  if  a  manure  shed  is  used  the  cistern  should  be  in  the 
shed.  The  gutter  should  be  connected  to  the  cistern  by  means  of  a 
drain  pipe  effectively  trapped  like  the  soil  pipe  in  a  house  and  so  arranged 
that  the  trap  may  be  easily  cleaned."  In  cities  with  sewer  facilities 
connection  is  made  directly  with  the  sewer,  dispensing  with  the  manure 
cistern. 

Often  the  concrete  stall  floors  are  covered  with  wood  so  that  the 
animals  do  not  come  in  direct  contact  with  the  concrete.  If  such  super- 
floors  are  provided,  they  should  be  made  of  heavy  two-inch  strips  three 
inches  wide  and  as  long  as  the  stall.  The  strips  are  fastened  together  by 
crosspieces  (ordinarily  flat  iron  strips)  so  that  a  space  of  about  one  half 
inch  remains  between  the  strips.  To  facilitate  ease  of  handling  it  is 
strongly  recommended  that  the  floor  be  made  in  two  long  pieces,  each 
half  the  width  of  the  stall,  and  fitting  closely  where  they  join.  In  this 
way  the  superfloor  can  be  lifted  up  while  the  concrete  is  being  cleaned ; 
the  crevices  between  the  wood  strips  can  be  readily  freed  from  manure 
by  means  of  a  heavy  stream  of  water  or  iron  rod.  If  the  crevices  are 
not  also  frequently  cleaned,  fly  larvae  will  develop  there  very  readily. 

Manure  and  odors  of  manure  will  attract  the  female  flies  even  though 
the  stable  is  somewhat  dark.  The  writer  believes  that  the  small  extra 
cost  of  screening  a  stable  against  flies  is  a  good  investment  since  it  not 
only  lessens  the  opportunity  for  flies  to  breed  but  also  adds  to  the  com- 
fort of  the  animals. 

Disposal  of  Manures.  —  Wherever  horse  manure  is  piled  up  in  the 
open  the  opportunity  is  given  for  flies  to  breed.  In  the  preceding  chap- 
ter it  was  pointed  out  that  an  average  manure  pile  weighing  about 
half  a  ton,  after  an  exposure  of  only  four  days  harbored  approximately 
450,000  fly  larvae.  As  before  stated  it  requires  only  about  four  days 
for  the  larvae  to  reach  full  growth,  after  which  they  begin  to  migrate  into 
the  drier  portions  of  the  heap  and  crawl  out  into  near-by  debris,  beneath 
platforms,  etc.  It  is  therefore  imperative,  if  fly  breeding  is  to  be  pre- 
vented, that  manure  be  protected  against  flies  from  the  beginning,  or 
that  it  be  rendered  undesirable  to  flies,  or  that  it  be  otherwise  disposed 
of. 

Under  ordinary  rural  conditions  the  most  practical  method  is  to 
remove  the  manure  to  the  field  daily.  A  cart  may  be  used  for  this 
purpose ;  it  is  daily  backed  up  against  the  stable  doorway,  the  manure 
thrown  in  and  carted  away  at  once  to  a  field  where  it  is  scattered.  This 
saves  much  time  in  handling  and  is  sound  agricultural  practice.  Since 
moisture  and  warmth  are  both  necessary  for  the  development  of  fly 
larvae  the  scattered  manure  cannot  serve  this  purpose. 


188        MEDICAL  AND  VETERINARY  ENTOMOLOGY 

If  more  desirable,  the  manure  may  be  placed  in  deep  narrow  trenches 
(preferably  concrete)  each  day  and  daily  covered  with  slaked  lime  and 
earth  and  allowed  to  rot.  The  disadvantage  is  that  the  manure  must 
be  dug  up  from  the  trenches  later  when  it  is  to  be  used  as  fertilizer. 
However,  the  former  method  is  more  practical  and  is  highly  recom- 
mended. The  Wisconsin  Bulletin  No.  221  states  :  "  Manure  is  never  so 
valuable  as  when  perfectly  fresh,  for  it  is  impossible  under  the  best 
system  of  management  to  prevent  all  loss  of  its  fertilizing  ingredients. 
For  this  reason,  whenever  possible,  the  manure  should  be  hauled  directly 
to  the  field  and  spread.  The  system  saves  time  and  labor  as  it  in- 
volves handling  but  once.  The  manure  will  be  leached  by  the  rain  and 
snow,  nevertheless  the  soluble  portion  will  be  carried  into  the  soil,  where 


^*'- 


FiG.  127.  —  Manure  bin  in  a  position  to  become  a  fly  breeding  cage,  instead  of  a  fly  pre- 
ventative. It  is  suggested  tfiat  the  lid  be  permanently  closed,  and  an  opening  made 
directly  from  the  stable  into  the  bin.  The  manure  pile  adjoining  the  bin  illustrates 
the  manner  of  disposal  before  the  bin  was  built. 

it  is  needed.  When  spread  in  a  thin  layer,  it  will  not  heat,  so  there 
will  be  no  loss  from  hot  fermentation,  and  where  manure  simply  dries 
out  when  spread  on  the  ground  there  is  no  loss  of  valuable  constituents." 
The  question  is  raised,  —  will  not  chickens  eat  the  maggots  and  thus 
keep  in  check  the  flies  in  manure  piled  up  in  the  barnyard  ?  It  must  be 
considered  that  manure  piled  up  sufficiently  deep  to  permit  fly  larvae 
to  develop  in  it  does  not  permit  chickens  to  scratch  their  way  through 
the  heap  and  consequently  they  can  only  destroy  a  small  fraction  of  the 
larvse ;  and  where  the  manure  pile  is  low  enough  for  chickens  to  scratch 
it  over  and  over,  the  fly  larvae  would  not  develop  anyway  owing  to  the 
dryness  and  lack  of  heat.  Furthermore,  it  is  not  safe  to  permit  chickens 
to  feed  on  maggots  owing  to  the  fact  that  the  larva  of  a  common  and 


HOUSE   FLY  CONTROL 


189 


dangerous  poultry  tapeworm  is  commonly  harbored  by  these  insects. 
Farmers  and  gardeners  who  wish  to  use  "rotted"  manure  for  fertilizing 
purposes  should  screen  the  heap  until  the  "  rotting  "  process  is  well 
under  way,  when  fly  breeding  will  be  reduced  to  a  minimum,  or,  as  has 
already  been  suggested,  the  manure  may  be  placed  in  trenches  and 
covered  with  lime  and  earth  whenever  fresh  manure  is  added  or  it 
may  be  stored  in  fly-tight  composting  pits. 

Manure  Bins.  —  Under  city  conditions   it  is   ordinarily  impracti- 
cable to  remove  manure  from  the  premises  daily,  hence  it  must  be 


Fig.  128.  —  A  properly  constructed  manure  bin  with  opening  directly  from  stable  into  bin. 
May  or  may  not  be  elevated  on  legs  to  facilitate  removal  of  manure  to  wagon.  Size  of 
bin  depends  on  number  of  horses  and  frequency  of  manure  removal. 


stored  temporarily  in  special  receptacles  or  bins.  Heretofore  stress 
has  been  laid  on  fly-tight  receptacles,  but  unless  exceptional  care  is 
exercised  in  operating  such  receptacles,  they  actually  become  fly-breed- 
ing cages.  The  writer  early  recognized  this  difficulty  and  suggested 
a  remedy  as  below  described. 

Fig.  127  illustrates  a  manure  bin  of  the  earlier  type.  The  manure 
pile  near  by  illustrates  the  manner  of  disp>osal  before  the  bin  was  erected. 
In  this  case  the  lid  of  the  bin  must  be  kept  open  while  the  manure  is 
being  transferred  to  it  from  the  stable,  and  during  this  time  flies  enter 
the  box  in  numbers,  and  when  the  lid  is  closed  they  are  trapped, 
deposit  their  eggs  and  soon  the  manure  is  reeking  with  maggots  and  if 
the  bin  is  not  cleaned  out  before  the  expiration  of  nine  or  ten  days 
myriads  of  flies  emerge  and  are  liberated  when  the  lid  is  opened. 


190        MEDICAL  AND   VETERINARY  ENTOMOLOGY 


The  bin  is  built  on  a  concrete  floor  to  prevent  rats  from  nesting 
underneath,  it  is  painted  with  creosote  inside  and  ventilation  is  pro- 
vided for  at  both  ends  by  means  of  screened  openings.  The  screen 
should  be  of  copper  wire  to  prevent  rapid  rusting.  The  front  of  the 
bin  is  provided  with  a  hinged  door  which  lifts  up  so  that  the  manure 
can  easily  be  removed.  The  dimensions  are  approximately  as  follows : 
length,  8  ft. ;  width,  4  ft. ;  height  in  front,  4  ft. ;  height  in  back,  5  ft. 
The  size  of  the  bin,  or  composting  pit  if  this  is  used,  depends,  of 
course,  on  the  number  of  horses  stabled  and  length  of  time  during 
which  the  manure  remains  in  storage.  It  may  be  estimated  that  the 
average  horse  produces  1|  cubic  feet  of  manure  per  day,  including 
bedding. 

To  prevent  the  bin  from  becoming  a  fly-breeding  cage,  the  wTiter 
recommends  that  the  top  be  permanently  closed,  i.e.  without  a  lid, 
and  that  the  manure  be  thrown  into  the  bin  directly  from  the  stable 
through  a  small  door  cut  through  the  side  of  the  stable  into  the  bin  near 
the  top  of  the  same  (Fig.  128).  This  opening  can  easily  be  provided 
with  a  small  sliding,  screened  door.  Furthermore  the  bin  should  be 
built  so  that  the  small  door  last  mentioned  can 
be  located  in  a  dark  part  of  the  stable,  thus 
further  preventing  flies  from  entering  the  bin. 
At  a  small  added  cost  fly  traps  can  be  attached 
at  the  ventilator  ends  of  the  bin  in  such  a  man- 
ner that  chance  flies  in  the  box  will  enter  these 
and  be  entrapped.  Because  the  flies  respond  to 
the  light  they  will  naturally  gather  at  the  ven- 
tilator ends  and  if  the  traps  are  baited  with  some 
material  attractive  to  the  flies,  there  is  an  added 
inducement  to  enter. 

Garbage  Cans.  —  The  writer  has  been  favor- 
ably impressed  with  the  type  of  combined  gar- 
bage can  and  fly  trap  invented  by  Professor  C.  F. 
Hodge.  By  his  permission  a  diagram  is  here 
given  (Fig.  129),  together  with  his  explanation  of 
the  same  (see  Nature  and  Culture,  July,  1911),  viz. :  "The  principle  of 
operation  is  that  hungry  flies  will  crawl  in  toward  the  smell  of  food 
through  any  dark  crack  and,  after  feeding,  will  fly  out  toward  the  light. 
They  enter  the  garbage  can  or  other  receptacle  by  smell,  and  attempt 
to  leave  by  sight.  It  is  necessary  to  have  the  cover  about  half  an 
inch  larger  in  diameter.  Three  pieces  of  sheet  iron  are  soldered  inside 
the  rim,  equidistant  apart  to  hold  it  up  a  crack,  and  keep  it  spaced 
out  from  the  rim  of  the  can  about  one  fourth  of  an  inch  all  around. 
In  a  swill  barrel,  nails  may  be  driven  into  the  rim  and  bent  over  to 
hold  the  cover  properly,  hut  direct  light  must  not  enter  this  crack.  Cut 
a  hole  in  the  cover  at  least  three  inches  in  diameter  and  fasten  the 
trap  over  this  opening  according  to  plain  directions  sent  out  with  each 


Fig.  129.  —  An  effective 
combination  garbage  can 
and  fly  trap.  (After 
Hodge.) 


HOUSE   FLY   CONTROL 


191 


trap.  With  everything  in  the  way  of  waste  food  material  put  into  this 
receptacle,  you  establish  a  '  focus,'  a  '  vacuum  cleaner  '  for  flies,  and 
properly  managed,  this  will  prove  exterminative." 

Where  ordinary  garbage  cans  are  used  and  certainly  every  household 
should  possess  a  garbage  receptacle  that  can  be  tightly  closed  against 
flies  (unless  above  plan  is  followed),  it  is  strongly  urged  that  all  liquids 
be  drained  from  the  refuse  before  disposing  of  it  and  that  the  solids 
be  wrapped  in  a  newspaper  before  placing  in  the  can.  In  this  way  fly 
breeding  in  garbage  cans  may  be  eft'ectually  prevented  and  an  act  of 
mercy  is  done  the  scavenger  and  others  as  well. 

Garbage  Collection  and  Disposal.  —  Not  only  must  the  garbage  can 
and  its  proper  use  be  insisted  upon  in  this  connection,  but  also  the 
proper  collection  of  the  garbage  by  the  scavenger.  Few  sights  are 
more  disgusting  than  that  of  an  open  garbage  wagon  reeking  with  its 
load  of  vile-smelling  offal  and  swarming  with  flies.  During  the  straw- 
berrv  season  it  is  a  matter  of  daily  occurrence  in  many  cities  to  see 


Fig.  130.  —  Flies  are  commonly  and  abundantly  distribvited  through  the  community  by 
poorly  arranged  garbage  wagons.  Properly  constructed,  closed,  city-owned  and  regu- 
lated garbage  wagons  must  take  the  place  of  the  above  pernicious  system. 

the  garbage  wagon  (Fig.  130)  traveling  side  by  side  with  the  strawberry 
wagon,  flies  crossing  from  one  to  the  other  without  restriction.  This 
is  certainly  revolting  if  not  also  a  menace  to  health.  Municipal  col- 
lection of  garbage  in  properly  constructed  city-owned  garbage  wagons 
is  the  only  solution  of  the  present  outrageous  common  system. 

No  more  sanitary  way  of  disposing  of  garbage  can  be  devised  than 
that  of  incineration.  The  garbage  dump  will  always  be  a  fly  producer, 
particularly  if  it  receives  manures  and  moist  offal. 


19^2        MEDICAL  AND   VETERINARY   ENTOMOLOGY 

The  Sanitary  Privy.  —  The  house  fly  breeds  in  enormous  numbers  in 
human  excrement  if  given  the  opportunity,  particularly  in  open,  shallow 
privies.  Not  only  are  the  newly  emerging  flies  laden  with  filth,  but  also 
flies  from  the  whole  neighborhood  which  have  congregated  about  such 
filth  places,  going  back  and  forth  between  these  and  the  family  kitchen 
and  dining  room.  This  outrage  against  civilization  calls  for  fly-proof 
privy  construction.  Many  small  communities  have  no  sewer  system, 
hence  the  use  of  the  old-fashioned  privy  (Fig.  131)  is  still  in  vogue, 
though  in  many  places  there  is  now  installed  the  septic  tank  system 
which  permits  of  sanitary  conveniences  in  the  home  at  a  reasonable 
cost.  The  septic  tank  places  within  the  reach  of  all  farm  homes  the 
establishment  of  modern  sanitary  conveniences  in  the  house,  free  from 
any  possibility  of  fly  breeding.  However,  the  appended  figures  of  a 
sanitary  privy  suggested  by  the  California  State  Board  of  Health 
Bulletin,  Vol.  6,  No.  6,  after  Stiles  (Fig.  132),  will  furnish  the 
reader  with  an  adequate  idea  for  the  construction  of  a  fly-tight 
privy.     It  must  be  borne  in  mind   that   simply  covering  the  excreta 


Fig.  131.  —  Privy,  swarming  with  flies,  adjoining  kitchen  door.  These  conditions,  invit- 
ing disease  and  insuring  the  pollution  of  food,  are  practically  duplicated  in  hundreds 
of  towns.      (By  courtesy  of  The  Survey.) 

with  dry  earth  does  not  prevent  flies  from  breeding  therein.  In  the 
absence  of  a  fly-tight  privy  it  is  advisable  to  add  quantities  of  chloride 
of  lime,  crude  oil,  or  kerosene  to  the  excreta  two  or  three  times  a 
week. 

Fly  Traps.  —  Unless  fly  traps  are  used  to  capture  the  flies  as  they 
emerge  from  their  breeding  place,  as  already  described,  such  measures 
are  ordinarily  only  excuses  for  the  more  important  cleaning-up  proc- 
ess ;  the  entrapped  flies  have  ordinarily  already  had  ample  opportunity 
to  carry  filth  and  germs  and  deposit  their  eggs.     However,  traps  may 


HOUSE   FLY   CONTROL 


193 


be  useful  adjuncts  to  other  more  permanent  corrective  measures,  — 
the  more  flies  captured  the  better,  but  the  trapping  should  begin  very 
early  in  the  spring  in  order  to  capture  the  early  flies  which  are  responsible 
for  the  later  multiplied  millions  of  the  same  species.  Many  good  fly 
traps  are  on  the  market  and  these  may  be  baited  with  milk  soaked 
bread,  stale  beer,  or  the  juice  of  crabs. 

Insecticides  on  Manure  Piles.  —  The  writer  is  constantly  requested 
to  recommend  insecticides  that  may  be  applied  to  manure  in  order  to 
either  destroy  fly  larvte  or  prevent  fly  breeding.  He  has  for  some  time 
consistently  refrained  from  making  such  recommendations,  because,  in 
the  first  place,  such  methods  seem  to  be  accepted  as  a  substitute  for 
cleaning  up,  and,  in  the  second  place,  owing  to  the  necessity  for  constant 
repetition,  applications  of  the  same  would  certainly  be  neglected. 
Furthermore  the  expense  of  the  daily  use  of  insecticides  in  efficient 
strengths  is  forbidding  to  the  man  of  ordinary  means. 

Ordinary  applications  of  the  usual  insecticides  prove  of  no  avail. 
The  cheapest,  and  at  the  same  time  the  most  effective,  preparations  must 
be  applied  two  to  five  times  as  strong  as  when  used  against  other  insects, 


Fig.   132.  —  A  sanitary  privy,  —  front  view  to  left ;    rear  and  side  view  to  right.      (After 

Stiles  and  Lumsden.) 


and  furthermore  the  larvse  cannot  be  easily  reached,  buried  as  they 
are  in  the  straw  and  manure.  In  the  face  of  these  conditions  the 
more  reliable  and  really  simpler  methods  already  mentioned  are  rec- 
ommended. 

Chemicals  used  to  destroy  the  larvae  may  be  roughly  divided  into 
two  classes,  viz.  (1)  contact  poisons,  and  (2)  stomach  poisons.     To  the 


194        MEDICAL  AND  VETERINARY  ENTOMOLOGY 

first  class  belong  such  preparations  as  kerosene,  chloride  of  lime,  etc. 
To  the  second  class  belong  the  arsenicals  represented  by  arsenate  of 
lead  and  paris  green. 

Where  the  manure  can  be  spread  out  to  a  depth  of  about  half  a  foot 
it  may  be  drenched  with  a  distillate  petroleum,  which  possesses  a  high 
flash  point,  i.e.  does  not  ignite  easily,  and  which  has  the  necessary 
insecticidal  value.  Kerosene  Emulsion  should  be  applied  at  the 
rate  of  one  part  of  the  oil  to  five  parts  of  water.  //  distillate  oils 
of  a  low  flash  yoint  are  used  about  stables  and  outbuildings,  the  danger 
from  fire  must  not  be  overlooked.  The  manure  so  treated  cannot  be  used 
for  fertilizing  purposes. 

Chloride  of  lime,  also  a  contact  insecticide,  applied  liberally  to  the 
manure  is  effective,  but,  like  the  above,  is  expensive  when  used  in 
proper  quantities. 

TABLE  XI 

Showing  the  Effect  of  Various  Insecticides  and  other  Materials  on 
Fully  Grown  House  Fly  Larv^ 

The  larvae  were  placed  in  shell  vials,  two  larvae  in  each,  ten  for  each  set.  The 
vials  were  capped  with  filter  paper  and  a  strip  of  the  same  material  soaked  in 
tap  water  was  placed  inside  with  the  larvae.  Check  sets  treated  with  tap 
water  were  rmi  in  connection  with  each  experiment.  Temperature  con- 
ditions were  favorable  in  all  cases.  Whenever  less  than  90  per  cent  of  the 
check  larvae  emerged  as  flies  the  entire  experiment  was  discarded.  Each 
material  was  given  at  least  two  tests,  ordinarily  by  different  persons. 


Name  of  Material 
Used 

Concentration 

No.  OF 
Larv^ 
Killed 

Name  of  Ma- 
terial Used 

Concentration 

No.  OF 

LARViE 

Killed 

Carbolic  acid        .     .     . 

2i% 

100% 

Lime  sulphur 

straight 

0 

Carbolic  acid 

1% 

90% 

Pyroligneous  acid 

straight 

0 

Creolin  .... 

2i% 

100% 

Creolin        .     .     . 

5% 

100% 

Boracic  acid 

saturated  solution 

100% 

Creolin        .     .     . 

!        10  % 

100% 

Kerosene     .     .     . 

straight 

100% 

Boracic  acid 

40%  solution 

90% 

Kerosene  emulsion 

1  to  10 

0% 

Borax 

powder 

80% 

Kerosene  emulsion 

1  to    8 

50% 

Formaldehyde 

4%, 

100% 

Kerosene  emulsion 

1  to    5 

100% 

Formaldehyde 

2% 

0 

Nicotine  sulphate 

40% 

80% 

Ferric  sulphate 

saturated  solution 

10% 

Nicotine  sulphate 

20% 

80% 

Tobacco  dust 

high  grade 

0 

Common  salt 

saturated  solution 

0 

Ferrous  sulphate 

saturated  solution 

0-10% 

Sodium  cyanide 

1%  solution 

100% 

Ferrous  sulphate 

10% 

0 

Sodium  cyanide 

xVof  1% 

0 

Ferrous  sulphate 

20% 

0 

Pyrethrum  powder 

straight 

80% 

Potassium  dichromate 

:  saturated  solution 

100% 

Gypsum 

straight 

0 

Potassium  dichromate 

20% 

100% 

Carbolate  of  lime 

straight 

100% 

Potassium  dichromate 

10% 

80% 

Potassium  dichromate 

5% 

40% 

Carbolate  of  lime 

mixed  with  manure 

20% 

Potassium  dichromate 

1% 

30% 

Chloronaphtholeum 

1  to  100 

100% 

Phenoco 

1  to  100 

20% 

Chloronaphtholeum 

1  to  200 

100% 

Phenoco 

1  to  200 

100% 

Chloronaphtholeum 

1  to  300 

30% 

Chloronaphtholeum 

1  to  400 

0 

Pyxol 

1  to  200 

50% 

C.N 

1  to  TOO 

100% 

Pyxol 

1  to  100 

0 

C.N 

1  to  200 

100% 

Pyxol 

1  to    50 

90% 

C.N 

1  to  500 

70% 

HOUSE  FLY  CONTROL  195 

The  use  of  arsenical  poisons  has  not  been  thoroughly  tested  by  the 
writer;  indeed  he  hesitates  to  recommend  these  materials  for  general 
use  because  of  the  danger  to  domesticated  animals  in  and  near  the 
barnyard  ;  however,  Newstead  ^  states  :  "the  application  of  paris  green 
(poison)  at  the  rate  of  two  ounces  to  one  gallon  of  water  to  either 
stable  manure  or  ashpit  refuse  will  destroy  99  per  cent  of  the  larvae. 
Possibly  a  smaller  percentage  of  paris  green  might  be  employed  with 
equally  good  results.  One  per  cent  of  crude  atoxyl  in  water  kills  100 
per  cent  of  fly  larvae."  The  application  of  either  of  these  substances 
might,  however,  lead  to  serious  complications  and  it  is  very  doubtful 
whether  they  could  be  employed  with  safety. 

In  an  experimental  study  of  a  large  number  of  insecticides  as  applied 
to  fly  larvae,  the  writer,  in  cooperation  with  several  of  his  students,  has 
obtained  the  above  results  (see  Table  XI). 

The  above  table  includes  only  a  partial  list  of  materials  tested  out 
in  the  laboratory,  and  indicates  that  there  are  a  number  of  remedies 
heretofore  advertised  as  efficient  in  the  control  of  fly  larvae,  now  proved 
to  be  without  virtue,  among  them  pyroligneous  acid,  gypsum,  and 
iron  sulphate.  On  the  other  hand  there  are  quite  a  number  of  materials 
which  have  proved  efficient,  notably  carbolic  acid  1  per  cent  to  2^  per 
cent,  creolin  2|  to  5  per  cent,  kerosene  emulsion  1  to  5  per  cent,  potassium 
dichromate  20  per  cent,  sodium  cyanide  (very  dangerous)  1  per  cent 
solution,  chloronaphtholeum  1  to  200,  "C.  N."  1  to  200,  and  boracic  acid 
in  saturated  solution.  The  U.  S.  Department  of  Agriculture  recom- 
mends applying  .62  pound  borax  or  .75  pound  calcined  colemanite  to 
every  eight  bushels  (10  cu.  ft.)  of  manure  immediately  on  its  removal 
from  the  barn.  The  borax  is  to  be  applied  by  means  of  a  flour  sifter 
to  the  outer  edges  of  the  pile  and  sprinkled  with  two  or  three  gallons 
of  water.     Hellebore  is  also  recommended. 

In  applying  these  materials  and  others  already  mentioned  for  the 
destruction  of  fly  larvae,  two  things  must  be  borne  in  mind,  namely 
(1st)  that  the  manure  pile  must  be  drenched  in  order  that  the  chemical 
may  reach  the  individual  larvae,  and  (2d)  what  effect  will  the  chemical 
have  on  the  fertilizing  value  of  the  manure  ? 

Hot  Water  Method.  —  It  is,  of  course,  well  known  that  manure  stored 
in  tight  vessels  and  covered  well  with  water  does  not  breed  house  flies. 
The  writer  has  also  carried  on  a  number  of  experiments  with  hot  water, 
particularly  in  such  cases  in  which  the  manure  is  already  inhabited  by 
fly  larvae  and  it  is  desired  to  use  the  same  or  remove  it.  Water  heated 
to  90°  C.  (195°  F.)  and  applied  in  saturating  quantities  destroys  all 
larvae.     At  85°  C.  and  below  all  continue  to  develop. 

Two  objections  are  commonly  raised  against  this  method  of  treat- 
ment :  (1st)  that  the  useful  bacteria  are  destroyed,  i.e.  that  the  manure  is 

1  Newstead,  R.,  1908.  Life  cycle  and  breeding  places  of  the  common 
house  fly  (Musca  domestica  Linn.)-  Annals  of  Tropical  Medicine  and  Para- 
sitology, Vol.  1,  No.  4,  pp.  507-520. 


196        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

rendered  sterile,  and  (2d)  that  all  other  desirable  constituents  are 
leached  out  by  the  water.  These  objections  are  not  altogether  well 
founded.  Not  all  of  the  useful  bacteria  by  any  means  are  destroyed 
by  the  hot  water  and  those  remaining  quickly  multiply  and  soon  render 
the  manure  as  good  as  ever.  In  the  second  place  the  leachings  may  be 
preserved  quite  easily  by  first  placing  the  manure  in  a  tight  shallow  box 
similar  to  those  used  by  plasterers  for  mixing  mortar,  and  adding  a 
spigot  or  simply  boring  a  large  hole  in  the  bottom  and  inserting  a  plug, 
thus  preserving  the  ingredients  until  allowed  to  flow  out  of  the  hole 
into  a  pail  to  be  applied  as  liquid  manure. 

The  above-described  method  is  particularly  useful  to  gardeners  and 
mushroom  growers  who  must  use  rotted  manure,  in  which  fly  larvae  of 
many  species  occur  very  abundantly. 

The  Fly  in  the  House  (Fly  Poisons).  ^ — Because  of  the  disease-trans- 
mitting powers  of  flies  they  should  be  kept  away  from  human  food. 
Fly  swatters  should  be  used  vigorously  and  daily.  Screens  must  con- 
tinue to  be  used  until  the  community  as  a  whole  learns  to  apply  the 
simple  measures  for  the  control  of  the  fly,  when  screens  will  no  longer 
be  needed,  and  that  time  is  not  far  oft'.  The  use  of  poisonous  (arsenical 
and  cobalt,  etc.)  preparations  upon  which  the  flies  may  feed  is  not 
recommended,  inasmuch  as  the  poisoned  insects  may  drop  into  foods, 
a  matter  perhaps  of  small  importance,  but  what  is  more  important,  many 
of  these  preparations  are  a  menace  to  human  life,  especially  to  small 
children.  The  writer  has  found  (as  already  suggested  by  others)  that 
formaldehyde,  properlv  used,  forms  a  very  good  substitute  for  arsenical 
or  cobalt  poisons.  Various  dilutions  and  combinations  were  tried, 
but  a  2  per  cent  solution  sweetened  somewhat  with  sugar  or  honey  (or 
even  without  sweetening)  proved  most  desirable.  Formaldehyde  is 
inexpensive  when  thus  used,  and  has  the  added  advantage  that  it  is 
relatively  not  poisonous  to  man  in  weak  concentrations,  and  may, 
therefore,  be  used  with  little  fear.  It  is  also  one  of  the  most  powerful 
germicides  known,  and  is  not  injurious  to  delicate  fabrics.  Formaldehyde 
is  ordinarily  purchased  in  from  38  to  40  per  cent  solutions  and  should 
be  diluted  with  water  to  about  2  per  cent  (add  about  twenty  times  as 
much  water).  The  solution  should  be  placed  in  shallow  vessels  on 
window  sills,  on  the  table  or  in  the  show  window.  It  is  not  an  easy 
matter  to  control  the  fly  in  a  dining  room  where  there  are  plenty  of 
liquids  for  food  and  drink,  such  as  water,  milk,  sweets,  etc.,  hence,  these 
should  be  removed  or  covered,  for  example,  in  the  evening  and  the  dishes 
of  formaldehyde  then  put  in  place  ;  the  flies  will  drink  the  poison  the  first 
thing  in  the  morning  and  the  end  will  be  readily  accomplished.  One 
is  thus  taking  advantage  of  the  fact  that  the  fly  seeks  something  to 
drink  early  in  the  morning.  Placing  a  piece  of  milk-soaked  bread  in 
the  dish  of  formaldehyde  adds  somewhat  to  the  efficiency.  During  the 
day  the  fly  poison  acts  best  when  placed  in  a  sunny  spot.  For  outdoor 
work  formaldehyde  is  equally  efficient,  but  must  be  made  inaccessible  to 


HOUSE  FLY  CONTROL  I97 

chickens,    birds    and   other    animals   by   screening  with   coarse-mesh 
wire. 

Various  fumes  created  by  burning  one  or  the  other  of  the  following 
materials  will  stupefy  the  flies,— pyreth rum  powder  (Persian  pyrethrum 
or  Chrysanthemum  cinerariafolium) ,  buhach,  dried  Jimson  weed  leaves 
(Datura  stramonium.)  mixed  with  crystals  of  saltpeter  (see  under  mos- 
quitoes), fumes  of  "cresyl,"  etc.  The  fly-fighting  committee  of  the 
American  Civic  Association  recommends  the  following:  "Heat  a 
shovel,  or  any  similar  article,  and  drop  thereon  20  drops  of  carbolic 
acid  ;  the  vapor  kills  the  flies." 

Other  Precautions.  —  It  is  highly  important  that  sick  rooms  be 
well  screened,  especially  in  cases  of  certain  transmissible  diseases, 
such  as  typhoid  fever,  tuberculosis,  etc.  For  the  protection  of  the  out- 
side world  any  flies  that  chance  to  find  their  way  inside  after  the  best 
precaution  has  been  exercised  should  be  killed  to  prevent  their  escape. 
Pus  rags,  bandages,  sputum  cloths,  and  the  like,  should  not  be  carelessly 
thrown  into  the  open  garbage  barrel  where  flies  freely  congregate.  It 
may  seem  unnecessary  to  even  mention  these  simple  sanitary  measures, 
but  the  writer  has  seen  the  grossest  neglect  in  matters  of  this  kind,  even 
where  better  judgment  should  have  prevailed. 

Natural  Enemies.  —  The  most  important  natural  enemy  of  the 
house  fly  is  the  fly  fungus,  Empusa  muscw,  first  described  by  DeGeer 
in  1872  (Howard)  and  rediscovered  annually  by  enthusiastic  human 
enemies  of  the  house  fly.  During  late  summer  and  autumn  and  through- 
out the  moist  winter  in  California,  dead  flies  are  frequently  found  cling- 
ing to  curtains  and  walls ;  the  abdomen  is  usually  greatly  distended, 
showing  distinct  bands  due  to  the  appearance  of  the  intersegmental 
tissue  brought  to  view  by  the  pressing  apart  of  the  darker  segmental 
rings.  ^  The  disease  is  commonly  known  as  fly  cholera. 

This  fly  fungus  originates  from  spores  which,  when  a  fly  is  attacked, 
produce  hypha,  thread-like  processes  which  enter  the  body  of  the  fly 
and  develop  a  mesh  work  of  threads,  producing  great  distension  of  the 
fly's  abdomen.  This  mycelium  later  evidently  sends  out  hyphee  through 
the  intersegmental  tissue,  which  hyphse  then  produce  spores  or  conidia. 
The  spores  are  then  separated  often  with  some  force,  and  may  produce 
a  sort  of  "halo"  about  the  now  dead  fly.  Other  flies  thus  become 
easily  infected.  The  writer  has  lost  experimental  colonies  of  flies  in 
great  numbers  in  this  way  in  less  than  two  weeks  after  the  appearance 
of  the  disease. 

Another  very  common  parasite  of  tne  fly  is  a  red  mite,  Acarus 
muscarum.  Often  three  or  four  of  these  mites  may  be  seen  as  tiny  red 
specks  on  the  head,  neck  or  thorax  of  the  house  fly.  Occasionally  they 
actually  retard  the  fly  in  its  flight. 

When  rearing  house  flies  from  pupae  collected  out  of  doors  one  is 
frequently  surprised  to  find  that  50  per  cent  or  more  give  rise  to  a 
tiny  dark  metallic  wasp  which  creeps  out  of  the  pupa  case  through  a 


198        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

minute  hole.  These  are  chalcidoid  wasps,  one  species  of  which  is  known 
as  Nasonia  brevicornis. 

While  house  flies  are  also  attacked  by  various  other  natural  enemies, 
such  as  spiders,  robber  flies,  toads,  lizards,  etc.,  their  generation  does 
not  seem  to  be  greatly  affected,  and  man  must  depend  more  and  more 
on  suppressing  the  breeding  places  of  the  pernicious  pest  or  suffer  the 
consequences. 

The  Community  Fly  Crusade.  — ■  Under  city  or  town  conditions  the 
crusade  against  the  fly  must  be  backed  up  by  the  intelligent  interest 
of  the  citizens.  Through  intelligent  cooperation  it  should  be  possible 
to  reduce  the  fly  population  of  any  city  or  town  by  95  per  cent  during 
the  course  of  a  single  summer,  and  if  action  is  taken  in  the  autumn  to 
eliminate  breeding  places  and  destroy  overwintering  flies,  the  following 
summer  could  be  made  practically  flyless. 

Numerous  crusades  against  the  housefly  have  been  conducted  in 
many  cities  in  the  United  States  with  good  results.  In  each  case  the 
work  has  usually  been  begun  by  an  organization,  already  in  existence, 
such  as  a  Women's  Club,  Civic  Club,  Chamber  of  Commerce  and 
occasionally  a  Board  of  Health.  Methods  of  procedure  are  usually 
outlined  by  competent  Medical  Entomologists,  Parasitologists,  Medical 
Officers  or  other  individuals. 

To  carry  out  the  suggested  permanent  preventive  measures,  etc., 
a  community  should,  to  begin  with,  have  an  appointed  staff  of  trained 
inspectors,  the  number  varying  with  the  size  of  the  community ;  four 
capable  men  working  in  pairs  can  cover  considerable  territory  very  well. 
No  community  should  be  without  regular,  trained  sanitary  inspectors 
under  the  direction  of  the  Board  of  Health.  The  position  of  sanitary 
inspector  should  carry  with  it  some  dignity,  and  should  be  filled  by  men 
instructed  in  practical  hygiene,  including  a  fair  knowledge  of  medical 
entomology,  owing  to  the  importance  of  insects  in  their  relation  to 
disease  transmission. 

The  best  results  will  always  be  secured  when  the  work  is  done  through 
the  Board  of  Health  with  as  many  civic  organizations,  schools,  clubs, 
etc.,  as  possible  in  intelligent  and  systematic  cooperation  to  spread  the 
propaganda.  The  active  assistance  of  the  school  children  may  well 
be  enlisted  for  the  sake  of  the  lesson  in  community  service.  However, 
little  can  be  said  in  favor  of  offering  prizes  for  a  given  quantity  of  flies. 
Let  the  children  be  taught  where  flies  originate,  their  habits,  etc., 
and  then  let  the  children  report  the  presence  of  flies,  say  by  counts, 
in  certain  situations,  stores,  homes,  etc.,  and  locate  and  report  breeding 
places  particularly.  There  will  be  just  as  much  interest  and  enthusiasm, 
the  ultimate  results  will  be  better  and  the  opportunity  to  deal  in  flies  is 
not  a  factor,  —  the  children  are  dealing  in  terms  of  cleanliness,  hygiene 
and  sanitation. 

"Fly  swatting"  only  serves  to  attract  the  attention  away  from  the 
real  issue,  namely,  the  control  of  breeding  places.     However,  a  wise. 


HOUSE   FLY  CONTROL 


199 


properly  guided  agitation  in  this  direction  in  the  winter  and  spring  would 
serve  to  reduce  the  early  crop  of  flies  materially,  and  the  interest  thus 
secured  could  gradually  be  won  over  to  the  side  of  civic  cleanliness  and 
the  slogan  will  have 
changed  from  "  swat 
the  fly"  to  "swat  the 
manure  pile." 

Communities  in 
which  a  campaign 
against  the  house  fly 
has  been  undertaken 
with  a  determination 
to  win  have  shown 
that  this  insect  can 
be  controlled,  and 
this  without  great 
labor  and  expense. 
The  problem  is  sim- 
pler than  many  are 
willing  to  admit. 
Hearty  cooperation 
is  essential.  Every- 
body is  concerned, 
and  everybody  will 
share  in  the  victory 
and  share  in  the  sav- 
ing of  financial  and 
vital  losses.  Remem- 
ber this,  —  the  pres- 
ence of  many  flies 
always  denotes  a  dirty 
enviromnent. 

Figure  133  illus- 
trates the  .type  of 
literature  used  by  va- 
rious communities  in 
their  crusade  against 
the  fly,  and  Fig.  134 
shows  a  part  of  the 
"House-fly  Exhibit  "at 
the  Baby  Saving  Show 
held  in  Oakland,  Cali- 
fornia, in  1914. 

Manure,  Stable  and  Fly  Ordinances.  —  Under  ordinary  conditions 
the  crusade  against  the  fly  must  also  be  a  matter  of  ordinance  backed  by 
the  intelligent  interest  of  the  citizens.     One  stable  owner  who  does  not 


Fig. 


133.  —  Literature,  bulletins,  etc.,  used  by  various  com- 
munities in  their  crusades  against  the  house  fly. 


200 


MEDICAL  AND   VETERINARY  ENTOMOLOGY 


HOUSE  FLY  CONTROL  201 

believe  in  the  "  notion  "  that  flies  originate  in  horse  manure  (and  there 
are  not  a  few  of  that  kind),  can  easily  supply  flies  for  several  adjacent 
city  blocks,  hence  there  must  be  some  ordinance  to  compel  action. 

Ordinances  must  be  practical  so  that  it  is  possible  to  comply  there- 
with, must  be  constitutional  and  must  provide  for  a  basis  for  conviction, 
i.e.  our  newer  manure  ordinances  will  point  out  that  the  presence  ot 
fly  larvse  or  pups  is  sufficient  evidence  that  the  provisions  of  the  ordi- 
nance have  not  been  complied  with. 

Ordinances  aimed  at  the  fly  nuisance  fall  under  three  heads,  namely, 
(1)  Stable  ordinances,  (2)  Manure  ordinances,  (3)  Food  ordinances 
(protection  against  dust  aiid  flies). 

Stable  Ordinances.  —  The  following  regulations,  according  to 
Howard,^  are  in  force  in  the  District  of  Columbia : 

''Sec  ISA.  No  person  owning,  occupying  or  having  use  of  any  stable,  shed, 
pen,  stall,  or  other  place  within  any  of  the  more  densely  populated  parts  ot  the 
District  of  Columbia,  where  animals  of  any  kind  are  kept  shall  permit  such  stable, 
shed  pen,  stall,  or  place  to  become  or  to  remain  filthy  or  unwholesome      _ 

"Sec  185  No  person  shaU  use  any  stable,  nor  shall  any  person  having  the 
power  and  authority  to  prevent  or  permit  any  person  to  use  any  stable  withm 
anv  of  the  more  densely  populated  parts  of  the  District  of  Columbia,  after  the 
first  dav  of  July,  1907,  unless  the  surface  of  the  ground  beneath  every  stall  and 
for  a  distance  of  four  feet  from  the  rear  thereof  be  covered  with  a  water-tight 
floor  laid  ^vith  such  grades  as  will  cause  all  fluids  that  fall  upon  it  to  tiow  as 
promptly  as  possible,  if  a  public  sewer  be  available,  into  the  public  sewer,  and 
if  a  pubhc  sewer  be  not  available,  to  that  portion  of  the  premises  where  they  wiU 
cause  the  least  possible  aimoyance.  _  ,    -u-  ^    (  a 

"Sec  ISC  Every  person  owning  or  occupying  any  building  or  part  oi  a 
building  within  any  of  the  more  densely  populated  parts  of  the  District  of 
Columbia  where  one  or  more  horses,  mules,  cows,  or  similar  animals  are  kept, 
shall  maintain  in  connection  therewith  a  bin  or  pit  for  the  reception  oi  manure, 
and,  pending  the  removal  from  the  premises  of  the  manure  from  the  animal  or 
animals  aforesaid,  shah  place  such  manure  m  said  bm  or  pit.  The  bm  or  pit 
required  by  this  regulation  shah  be  located  at  a  point  as  remote  as  practicable 
from  any  dwelling,  church,  school  or  similar  structure,  owned  or  occupied  by  any 
person  or  persons  in  the  neighborhood  of  said  bin  or  pit,  other  than  the  owner  or 
occupant  of  the  building  or  part  of  building  aforesaid  and  as  remote  as  prac- 
ticable from  any  pubUc  street  or  avenue ;  shall  be  so  constructed  as  to  exclude 
rain  water,  and  shall  in  all  other  respects  be  water-tight  except  as  it  may  be 
connected  with  the  public  sewer  or  as  other  definite  provisions  may  be  made  tor 
cleaning  and  flusliing  from  time  to  time ;  shall  be  provided  with  a  suitable  cover 
and  constructed  so  as  to  prevent  in  so  far  as  may  be  practicable  the  ingress  and 
egress  of  flies.  No  bm  or  pit  shall  be  constructed  the  bottom  of  which  is  bcxow 
the  level  of  the  surface  of  the  surrounding  earth  unless  it  be  of  substantial 
masonry  and  connected  with  the  pubhc  sewer.  The  provisions  of  this  paragraph 
shaU  take  effect  from  and  after  the  expiration  of  three  months  immediately 
foUowing  its  promulgation.  ,    ., ,.  ^    t     u  •^A 

"Sec.  ISD.  No  person  owning  or  occupying  any  buildmg  or  part  ot  a  bund- 
ing located  within  any  of  the  more  densely  populated  parts  of  the  District  of 
Columbia  in  which  building  or  part  of  a  building  any  horse,  mule,  cow  or  similar 
animal  is  kept,  shaU  keep  any  manure,  or  permit  any  manure  to  be  kept,  in  or 
upon  any  portion  of  the  premises  other  than  the  bm  or  pit  provided  tor  that 
1  Howard,  L.  O.,  1911.  The  housefly,  disease  carrier.  Frederick  A. 
Stokes  Co.,  New  York,  xix  +  312  pp. 


202        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

purpose ;  nor  shall  any  person  aforesaid  allow  any  such  bin  or  pit  to  be  over- 
filled or  to  be  needlessly  uncovered. 

"Sec.  18E.  The  provisions  of  paragraphs  C  and  D  shall  not  apply  to  the 
keeping  of  manure  from  horses  when  such  manure  is  kept  tightly  rammed  into 
the  well-covered  barrels  for  the  purpose  of  removal  in  such  barrels. 

"Sec.  18F.  No  person  shall  permit  any  manure  to  accumulate  on  premises 
under  his  control  in  such  a  manner  or  to  such  an  extent  as  to  give  rise  to  objec- 
tionable odors  upon  any  pubUc  highway  or  upon  any  premises  owned  or  oc- 
cupied by  any  person  other  than  the  person  owning  or  occupying  the  premises 
on  which  said  manure  is  located.  Every  person  having  the  use  of  any  manure, 
in  any  of  the  more  densely  populated  parts  of  the  District  of  Columbia,  shall 
cause  all  such  manure  to  be  removed  from  the  premises  at  least  twice  every  week 
between  June  first  and  October  thirty-first,  inclusive  of  each  year,  and  at  least 
once  every  week  between  November  first  of  each  year  and  May  thirty-first 
of  the  following  year,  both  dates  inclusive. 

"Sec.  18G.  Every  person  using  witliin  the  District  of  Columbia  any  build- 
ing, or  any  portion  of  a  building,  in  the  city  of  Washington,  or  in  any  of  the  more 
densely  populated  suburbs  thereof,  as  a  stable  for  one  or  more  horses,  mules  or 
cows,  shall  report  that  fact  to  the  health  officer  in  writing,  within  thirty  days 
after  this  regulation  takes  effect,  giving  his  or  her  name,  and  the  location  of  such 
stable,  and  the  number  and  kind  of  the  animals  stabled  therein ;  and  thereafter 
every  person  occupying  any  building,  or  any  portion  of  a  building,  in  the  city  of 
Washington,  or  in  any  of  the  more  densely  populated  suburbs  thereof,  for  the 
purpose  aforesaid,  shall  report  in  like  manner  his  or  her  name  and  the  location  of 
said  stable,  and  the  number  and  kind  of  animals  stabled  therein,  witliin  five 
days  after  the  begmning  of  his  or  her  occupancy  of  such  buildings ;  provided, 
that  stables  recorded  at  the  Health  Office  as  parts  of  dairy  farms  in  the  District 
of  Columbia  need  not  be  so  reported. 

"Sec.  18H.  No  person  who  has  removed  manure  from  any  bin  or  pit,  or  any 
other  place  where  manure  has  been  accumulated,  shall  deposit  such  manure  in 
any  place  within  any  of  the  more  densely  populated  parts  of  the  District  of 
Columbia  without  a  permit  from  the  health  officer  authorizing  him  so  to  do  and 
then  only  in  accordance  with  the  terms  of  such  permit.  The  provisions  of  this 
paragraph  shall  not  apply  to  the  distribution  of  manure  over  lawns  and  parking 
when  such  manure  has  been  so  thoroughly  rotted  or  decomposed  that  its  dis- 
tribution gives  rise  to  no  offensive  odors  on  adjacent  properties  or  on  pubHc 
thoroughfares." 

The  stable  ordinance  in  force  in  Berkeley,  California,  contains  the 
following  sections :  — 

"Sec.  3.  Where  the  premises  on  which  any  stable  barn,  shed  or  stall  is 
maintained  in  which  any  horse,  mule  or  cow  is  kept,  fronts  on  a  street  in  which  is 
constructed  a  sewer  the  following  requirements  shall  be  compUed  with,  viz. : 
The  drainage  from  all  single  and  box  stalls  where  a  horse,  mule  or  cow  is  kept  or 
housed,  must  in  all  cases  be  connected  to  the  street  sewer.  The  floor  of  all 
said  stalls  must  be  made  impervious  to  water,  and  the  drainage  from  said  stalls 
must  be  conducted  to  the  sewer  either  in  tile  or  cement  gutters,  of  a  radius  of 
not  less  than  two  inches.  The  said  gutters  shall  discharge  into  a  3-inch  or 
4-inch  trap  before  entering  the  main  sewer.  The  trap  must  be  protected  in  all 
cases  by  a  strainer  and  be  easy  of  access  for  cleaning  purposes. 

"Sec.  5.  All  stables,  sheds,  barns,  stalls,  corrals,  or  stable  yards  in  which 
any  horse,  mule  or  cow  is  kept  shall  be  thoroughly  cleaned  out  at  the  following 
intervals  of  time :  Where  stables,  barns,  sheds,  stalls,  corrals,  or  stable  yards 
exist,  they  shall  be  cleaned  out  at  least  every  day.  The  manure,  offal,  soiled 
straw  or  other  refuse  matter  from  all  stables,  sheds,  corrals  or  stable  yards  shall 


HOUSE   FLY  CONTROL  203 

be  placed  immediately  upon  removal  from  such  stable,  bam,  shed,  stall,  corral 
or  stable  yard  in  closely  covered  metal  or  metal-lined  receptacles,  and  kept 
covered  until  destroyed  or  removed  from  the  premises.  The  contents  of  such 
receptacles  shall  be  removed  therefrom  and  disposed  of  at  least  twice  a  week." 

Another  type  of  stable  ordinance  requires  a  permit  for  the  erection 
and  use  of  stables,  etc.,  and  provides  for  inspection  of  the  same  by  the 
score  card  system.  The  following  is  suggested  by  Mr.  Carl  L.  A. 
Schmidt,  City  Bacteriologist  of  Berkeley  : 

"Section  1.  No  person,  firm  or  corporation  shall  o\\ti,  conduct,  operate, 
manage,  or  maintain  any  stable  for  the  use  of  horses,  cows  or  other  animals  with- 
out first  obtaining  a  permit  therefor  from  the  Health  Officer  in  accordance  with 
the  conditions  in  this  ordinance  hereinafter  provided,  which  permit  shall  be 
posted  in  a  conspicuous  place  in  the  stable. 

"Section  2.  Any  person,  firm,  or  corporation  desiring  a  permit  to  own,  con- 
duct, operate,  manage  or  maintain  a  stable  for  the  use  of  horses,  cows  or  other 
animals  shall  first  make  application  therefor  to  the  Health  Officer,  stating  the 
name  and  residence  of  the  applicant,  the  exact  location  of  the  stable  for  which  he 
desires  a  permit  and  the  kind  and  number  of  animals  to  be  kept  therein. 

"Section  3.  Upon  receipt  of  proper  application  as  provided  in  Section  2  it 
shall  be  the  duty  of  the  Health  Officer  or  his  authorized  representative  to  visit 
and  inspect  the  stable  for  which  application  has  been  made,  and  to  report  to  the 
Health  Officer  the  sanitary  condition  of  the  stable  on  a  score  card,  the  form  of 
which  is  hereinafter  pro^dded,  leaving  a  duplicate  copy  on  the  premises  inspected. 

"Section  4.  The  score  card  used  by  the  Sanitary  Inspector  as  provided  in 
Section  3  shall  be  printed  in  the  following  form  : 

CITY  OF  .  .  .  HEALTH  DEPARTMENT 
Stable  Scoke  Card 

Owner  or  Manager  of  Stable        

Location 

No.  of  horses No.  of  cows  ....  No.  of  other  animals 

Board  or  Private         

Date  of  Inspection 

Score 
Perfect  Allowed 

L   Character  of  building 10 

If  of  first  class  construction  of  frame  or  masonry      ...         10 

If  poorh^  constructed        5 

If  dilapidated 2 

2.  Floors,  cement  with  proper  gutters  and  catch  basin  and 

sewer  or  cesspool  connection 10 

Cement  broken 2 

Cement  badly  laid 5 

Wood  tightly  laid 8 

Wood  open  cracks 0 

3.  Manure  box,  strictly  fly-proof 50 

Manure  box,  any  part  open 5 

Manure  box,  tight  without  vent 40   ■ 

4.  Surroundings  perfectly  clean 30 

If  there  is  water  on  lot 10 

If  there  is  manure  scattered  about 3 

If  premises  are  disorderly _5 

100 


204        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

If  maggots  or  fly  pupse  are  found  on  premises,  score  will  be  limited  to  49. 
If  doors  are  not  properly  cleaned,  deduct  5  from  total.  Filthy  catch  basin, 
deduct  5  from  total. 

^^ Section  5.  If,  after  inspection,  the  apphcant's  score  shall  be  over  50,  the 
Health  Officer  shall  issue  to  the  appUcant  a  permit,  which  shall  be  numbered 
consecutively.  If  the  apphcant's  score  be  below  50,  the  Health  Officer  shall  send 
to  the  applicant  a  notice  to  improve  the  sanitary  condition  of  his  stable  so  that 
his  score  shall  be  above  50  within  a  period  of  7  days.  Failure  to  do  this  shall 
constitute  a  violation  of  this  ordinance. 

"Sectio7i  6.  It  shall  be  the  duty  of  the  sanitary  inspector  to  inspect  each 
stable  within  the  City  of  ...  at  least  once  every  three  months  or  oftener  at  his 
discretion  and  to  file  the  score  and  record  of  such  inspection  in  the  Health  Office. 
Two  consecutive  inspections  of  any  stable  showing  a  score  of  less  than  50  shall 
cause  the  Health  Officer  to  revoke  the  permit  of  the  stable,  and  the  person,  firm 
or  corporation  owning,  conducting,  operating,  managing  or  maintaining  such 
stable  shall  be  guilty  of  violating  this  ordinance." 

Manure  Ordinances.  —  Inasmuch  as  95  per  cent  of  our  house  flies 
emanate  from  horse  manure,  ordinances  regulating  the  disposal  of  such 
material  are  imperative.  Municipal  collection  and  disposal  of  manure 
is  highly  desirable.  There  is  no  reason  why  the  city  could  not  require 
that  all  manure  be  collected  by  authorized  scavengers.  The  manure 
is  then  either  to  be  incinerated  or  properly  stored  or  piled  in  some 
designated  spot.  It  is  far  more  preferable  that  a  city  have  one  very 
large  municipal  manure  pile  and  know  where  it  is,  than  to  have  500 
or  more  smaller  heaps  in  many  out-of-the-way  places  in  all  parts  of 
the  city.  The  manure  can  be  adequately  treated  in  the  former  case 
and  later  sold  at  a  price  that  would  assist  materially  in  clearing  the 
cost  of  municipal  collection.  The  following  ordinance  constructed  by 
the  writer  in  cooperation  with  Dr.  J.  N.  Force  of  the  Berkeley  (Cal.) 
Board  of  Health,  is  suggested : 

Ordinance  No.  .  .  . 

Regulating  the  Disposal  of  Manure  and  Other  Refuse  Matter  from  Buildings  or 
Yards  where  Animals  are  kept  within  the  City  Limits  of  .  .  . 

Be  it  ordained  by  the  Council  of  the  City  of  ...  as  follows : 

"Section  1.  The  manure,  offal,  soiled  straw  or  other  refuse  matter  from  all 
buildings  or  yards  where  animals  are  kept  shall  be  collected  at  least  once  daily 
and  shall  be  disposed  of  by  one  of  the  followdng  methods  : 

(a)  Said  refuse  may  be  stored  in  ventilated  bins  or  other  receptacle  of  such 
construction  approved  by  the  Board  of  Health  as  to  prevent  the  ingress  of  flies 
and  other  vermin,  said  bin  to  be  emptied  at  least  once  a  week,  or 

(6)  Said  refuse  may  be  removed  from  the  premises  at  least  once  a  day  by  an 
authorized  scavenger  and  disposed  of  in  a  manner  approved  by  the  Health  OflScer. 

(c)  Said  refuse  may  be  spread  in  a  layer  not  over  four  (4)  inches  in  depth 
on  the  surface  of  the  ground. 

"Section  2.  No  manure  shaU  be  used  for  fertiUzing  purposes  within  the  city 
limits  of  .  .  .  which  has  not  been  rendered  free  from  live  maggots  or  fly  pupse 
by  treating  with  saturating  quantities  of  water  at  a  temperature  of  195  deg. 
Fahrenheit,  or  some  other  method  approved  by  the  Health  Officer. 


HOUSE   FLY  CONTROL  205 

"Section  3.  The  presence  of  live  maggots  or  fly  pupae  in  any  collection  of 
refuse  found  in  the  City  of  .  .  .  shall  be  'prima  facie  evidence  that  the  provisions 
of  this  ordinance  have  not  been  complied  with. 

"Section  4.  It  is  hereby  made  a  duty  of  the  Commissioner  of  PubUc  Health 
and  Safety  or  any  Sanitary  Inspector  or  Police  Officer  to  provide  for  the  inspec- 
tion of  all  premises  where  animals  are  kept  in  the  City  of  .  .  .  and  examine  any 
manure  or  other  refuse  matter  to  determine  the  presence  of  live  maggots  or  fly 
pupse. 

"Section  5.     (Penalty  clause.) 

"Section  6.  All  other  ordinances  and  parts  of  ordinances  in  conflict  with  this 
ordinance  are  hereby  repealed." 

According  to  Howard  (loc.  cit.)  the  following  regulations  concerning 
manure  are  in  force  in  the  District  of  Columbia : 

"Section  3.  That  manure,  accumulated  in  great  quantities;  manure,  offal, 
or  garbage  piled  or  deposited  within  300  feet  of  any  place  of  worship,  or  of  any 
dwelling,  or  unloaded  along  the  line  of  any  railroad,  or  in  any  street  or  public 
way ;  cars  or  flats  loaded  with  manure,  or  other  offensive  matter,  remaining  or 
standing  on  any  railroad,  street  or  liighway  in  the  cities  of  Washington  or 
Georgetown,  or  in  the  more  densely  populated  suburbs  of  said  cities,  are  hereby 
declared  nuisances  injurious  to  health;  and  any  person  who  shall  pile  or  deposit 
manure,  offal,  garbage,  or  any  offensive  or  nauseous  substance  within  300  feet 
of  any  inhabited  dwelling  within  the  limit  of  said  cities  or  their  said  suburbs, 
and  any  person  who  shall  unload,  discharge  or  put  upon  or  along  the  line  of  any 
railroad,  street  or  highway,  or  public  place  within  said  cities  or  their  suburbs 
any  manure,  garbage,  offal,  or  other  offensive  or  nauseous  substances  within 
300  feet  of  any  inhabited  dweUing,  or  who  shall  cause  or  allow  cars  or  flats 
loaded  with  or  having  in  or  upon  them  any  such  substance  to  remain  or  stand  in 
or  along  any  railroad,  street  or  highway  within  the  limits  of  said  cities  or  their 
suburbs  within  300  feet  of  any  inhabited  dwelling,  and  who  shall  fail,  after  notice 
duly  served  by  this  board,  to  remove  the  same,  shall,  upon  conviction  thereof, 
be  fined  not  less  than  five  nor  more  than  twenty-five  dollars  for  every  offense." 

Extract  from  Article  IX,  Police  Regulations : 

"Sec.  10.  No  person  shall  remove  or  transport  any  manure  over  any  public 
highway  in  any  of  the  more  densely  populated  parts  of  the  District  of  Columbia 
except  in  a  tight  veliicle,  wliich  if  not  closed  must  be  effectually  covered  with 
canvas  so  secured  to  the  sides  of  the  vehicle  as  to  prevent  the  manure  from  being 
dropped  while  being  removed,  and  so  as  to  limit  as  much  as  practicable  the 
escape  of  odors  from  said  manure. 

"Sec.  20.  Manures  may  be  deposited  in  pits  below  the  surface  of  alleys  that 
are  not  less  than  fifteen  feet  wide,  but  the  pit  must  not  extend  more  than  four 
feet  beyond  the  building  line.  The  walls  must  be  substantial  and  water-tight, 
with  stone  or  iron  coping,  bedded  in  cement,  set  fair  with  the  surface  of  the  alley. 
They  must  be  covered  with  heavy  wrought-iron  doors,  flush  with  the  alley  pave- 
ment or  surface,  sufficiently  strong  to  carry  heavily  loaded  carts  or  other  vehicles, 
and  provided  with  ventilation  by  means  of  a  flue  inside  of  the  stable  and  extend- 
ing above  the  roof  of  the  same,  and  they  must  be  drained  by  sewer  connections, 
as  directed  by  the  Inspector  of  Plumbing." 

Food  Ordinances.  —  Foods  must  be  protected  against  dust  and  flies, 
hence  merchants  dealing  in  food  products  must  be  required  to  carry  out 
such  measures.  But  it  is  manifestly  unfair  to  compel  merchants  to 
protect  their  wares  against  flies  if  stable  owners  who  are  responsible 


206        MEDICAL  AND  VETERINARY  ENTOMOLOGY 

for  the  production  of  the  flies  are  not  compelled  to  do  anything  to  pre- 
vent the  same. 

The  Berkeley  (Cal.)  food  ordinance  includes  the  following  section : 

"Sec.  3|.  Every  manager,  owner,  or  other  person  keeping,  maintaining  or 
being  in  charge  or  control  of  any  store,  market,  stall,  shop,  bakery,  vehicle,  or 
other  place  where  any  of  the  foods  or  food  products  mentioned  in  Section  2  and 
Section  3  of  this  ordinance  are  prepared  for  sale,  stored  for  sale,  offered  for  sale 
or  sold,  or  where  food  which  is  prepared  for  immediate  consumption  is  prepared 
for  sale,  stored  for  sale,  offered  for  sale  or  sold,  shaU  cause  such  food  or  food 
products  to  be. screened  in  such  manner  as  to  prevent  flies  and  other  insects 
from  obtaining  access  to  such  food  or  food  products,  and  to  prevent  handling 
of  the  same  by  patrons  or  prospective  purchasers. 

Howard  (loc.  cit.)  cites  the  following  regulation  for  the  District  of 
Columbia  relating  to  food  : 

"Every  manager  of  a  store,  market,  dairy,  caf6,  lunch  room,  or  any  other 
place  in  the  District  of  Columbia,  where  food,  or  a  beverage,  or  confectionery,  or 
any  similar  article,  is  manufactured  or  prepared  for  sale,  stored  for  sale,  offered 
for  sale,  or  sold,  shall  cause  it  to  be  screened  effectually,  or  effectually  pro- 
tected by  power-driven  fan  or  fans,  so  as  to  prevent  flies  and  other  insects  from 
obtaining  access  to  such  food,  beverage,  confectionery  or  other  article  free  from 
flies  and  other  insects  at  all  times.  Any  person  violating  the  provisions  of  this 
regulation  shall,  upon  conviction  thereof,  be  punished  by  a  fine  of  not  more 
than  twenty-five  dollars  for  each  and  every  offence.  This  regulation  shall  take 
effect  from  and  after  the  expiration  of  thirty  days  immediately  following  the 
date  of  its  promulgation." 


CHAPTER   XV 


BLOOD-SUCKING  MUSCIDS 

(Tsetse  Flies,  Stable  Flies,  Horn  Flies) 

A.   Tsetse  Flies 
Family  MuscidoB,  Genus  Glossina 

Habits.  —  The  tsetse  flies  are  commonly  regarded  as  the  world's 
most  dangerous  insects,  and  this  with  much  reason,  for  the  African 
sleeping  sickness,  one 
of  the  most  dreaded 
diseases,  is  transmitted 
by  these  flies.  For- 
tunately, however,  the 
tsetse  flies  are  found 
solely  in  Africa  and 
there  only  in  certain 
restricted  areas. 

The  tsetses  are 
typical  intermittent 
blood-sucking  insects ; 
in  this  habit  both 
sexes  partake,  and  it 
is  said  that  they  bite 
not  only  during  the 
day,  but  also  at  night 
when  the  moon  is 
bright.  Their  flight 
is     very     rapid     and 

direct.         They      occur    Fig.   135.  —  GZossmapaZ/^ahs  (tsetse  fly),  carrier  of  African 
,1  1       xi        1  sleeping  sickness.      X  3.6. 

most  abundantly  along 

heavily  wooded  watercourses,  where  big  game  animals  abound,  espe- 
cially the  African  buffalo,  antelope,  etc.  Still  other  species  occur  most 
commonly  in  less  thickly  wooded  dry  localities. 

Structural  Characteristics.  —  The  tsetse  flies  ^  belong  to  the  genus 

1  The  writer  has  gathered  data  for  this  chapter  by  an  examination  of  the 
tsetse  fly  collections  and  exhibits  in  the  Liverpool  School  of  Tropical  Medi- 
cine, the  British  Museum  and  the  International  Hygiene  Exhibit  held  in  Dres- 
den in  1911. 

207 


208 


MEDICAL  AND  VETERINARY  ENTOMOLOGY 


Glossina,  which  includes  medium-sized  to  large  flies,  —  from  the  size 


of  a  house  fly  to  that  of  a  blow  fly. 
the  body  is  distinctly  wasplike,  i.e. 


Fig.  136.  —  Wing  of  a  Glossina  flj\  I",  auxiliary  vein  ; 
I  to  VI  =  first  to  sixth  longitudinal  veins;  A,  an- 
terior transverse  vein  ;  B,  posterior  transverse  vein  ; 
C,  anterior  basal  transverse  vein  ;  D,  posterior  basal 
transverse  vein;  1",  1*,  P,  first,  second  and  third 
costal  cells ;  2,  marginal  cell ;  3,  submarginal  cell ; 
4,  diskal  cell ;  5,  6,  7,  first,  second  and  third  posterior 
cells ;  8,  anterior  basal  cell ;  9,  posterior  basal  cell ; 
10,  anal  cell.      (Nomenclature  after  Austen.)       X  8. 


They  are  brownish  black  in  color, 
with  constricted  waist  (Fig.  135). 
The  wings  when  at  rest 
are  closed  scissors-like 
(not  unlike  the  Texas 
screw  worm  fly)  and  pro- 
ject beyond  the  abdomen. 
The  wing  venation  (Fig. 
136)  is  characteristic 
"especially  in  the  course 
of  the  fourth  longitudinal 
vein.  The  anterior  trans- 
verse vein  is  very  oblique. 
The  bend  in  the  course  of 
the  fourth  vein,  before  it 
meets  the  anterior  trans- 
verse vein,  is  absolutely 
diagnostic  "  (Stephens 
and  Christophers).  The  palpi  are  more  than  half  as  long  as  the  pro- 
boscis, which  points  bayonet-like  in  front  of  the  head.  The  antennal 
arista  is  plumose  only  on  the  upper  side  (Fig.  L37).  The  mouth  parts 
consist  of  the  labium  which  ensheaths  the 
two  piercing  setse,  —  the  dorsally  located  la- 
brum  and  the  inner  hypopharynx,  as  in  Sto- 
moxys.  The  characteristic  "onion  shaped" 
bulb  is  conspicuously  located  at  the  base  of 
the  proboscis  (Fig.  138). 

Life  History.  —  The  tsetse  flies  are  vi- 
viparous, depositing  well-advanced  larvae ; 
indeed,  these  are  fulh^  grown  and  pupate 
within  a  few  hours  after  extrusion.  The 
flies  are  said  to  have  a  striking  dislike  for 
excrementous  matter,  and  the  larvse  are  or- 
dinarily deposited  in  the  root  tangles  of  the 
banana,  mangroves  and  other  tropical  vege- 
tation. The  time  required  for  the  pupal 
stage  is  from  six  to  eight  weeks. 

The  pupse  (Fig.  139)  have  striking  pos- 
terior protuberances  of  the  terminal  segments. 
These  are  so  situated  as  to  produce  an  in- 
closure  for  the  larval  stigmata. 

Tr3rpaiiosomiasis.  - —  The  tsetse,  or  Glossina,  flies  are  most  impor- 
tant carriers  of  the  Trypanosoma  of  warm-blooded  animals.  The  term 
Trypanosomiasis  applies  to  all  diseases  produced  by  flagellate  Proto- 
zoan parasites  of  the  genus  Trypanosoma,  and  includes  such  diseases 


Fig.  137.  — Antenna  of  a  Glos- 
sina fly,  sho'wing  arista  with 
branched  hairs.  (Much  en- 
larged.) 


BLOOD-SUCKING   MUSCIDS 


209 


as  African  sleeping  sickness,  nagana,  surra,  etc.  The  trypanosomes 
belong  to  the  Class  Zoomastigophora  and  to  the  order  Trypanosoma- 
tida,  are  miscroscopic,  elongate,  more  or  less  spindle-shaped,  blood, 
lymph  or  cerebrospinal  fluid  inhabit- 
ing parasites,  found  in  many  species 
of  vertebrate  animals,  from  fish  to 
man,  and  apparently  not  all  species 
are  pathogenic.  At  or  near  the 
middle  of  these  spindle-shaped  or- 
ganisms lies  an  oval  or  round  body, 
the  nucleus;  anterior  to  this  is  usu- 
ally the  rather  long  filamentous  ap- 
pendage, the  flageUum.,  which  can  be 
traced  back  along  the  border  of  a 
flaplike  structure,  or  undulating  mem- 
brane, to  a  body  considerably  smaller 
than  the  nucleus,  lying  in  the  pos- 
terior end,  the  blepharoplast  (Fig.  lb). 
Immediately  adjacent  to  the  bleph- 
aroplast there  is  often  a  vacuole, 
and  distributed  throughout  the  body 
of  the  trypanosome  are  distinct  chro- 
matin bodies  or  points. 

The  Trypanosoma  increase  in  the 
vertebrate  host  by  longitudinal  divi- 
sion.    Both  the  nucleus  and  the  blepharoplast  divide,  and  the>  flagel- 
lum  splits  into  two,  or  in  some  species  a  new  fiagellum  originates  from 


ph4Vun> 


Fig.  138. 


Mouth  parts  of  a  Glossina  fly. 
X  17. 


Fig.   139.  —  Pupse  of  the  Glossina  fly.       X  4.8. 


the  new  blepharoplast.  Thus,  in  the  latter  case,  the  flagellum^is^first 
located  posteriorly  and  migrates  anteriorly  as  the  organism  grows  older. 
In  Trypanosoma  leioisi  there  may  be  found  a  rosette.     The  develop- 


210       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

mental  stages  which  are  undergone  in  the  intermediary  hosts  are  not 
well  known,  but  there  is  certainly  a  series  of  changes  undergone  within 
the  insect  host. 

There  are  also  described  male  forms  said  to  be  "  excessively  slender, 
staining  deep  blue,  with  a  sharply  defined,  rather  long,  chromatin-rich 
nucleus ;  more  actively  motile  than  other  forms ;  '  also  female  forms  ' 
with  short  flagellum  membrane,  little  folded,  two  or  three  times  as  broad 
as  other  forms  ;  staining  a  light  blue ;  have  few  or  no  granules,  and  the 
nucleus  is  spherical"  (Stephens  and  Christophers).  Besides  these 
there  are  also  described  indifferent  forms,  "  the  most  numerous  form, 
nucleus  not  sharply  defined  and  the  protoplasm  containing  numerous 
granules ;  "    also  encysted  forms,  latent  forms  and  involution  forms. 

The  first  trypanosome  was  discovered  by  Valentin  in  1841  in  the 
blood  of  the  salmon.  The  name  Trypanosoma  ^  was  given  to  these 
organisms  by  Gruby  in  1842-43.  The  attention  was  not  called  to  try- 
panosomes  of  mammals  until  the  work  of  Lewis  in  1878,  on  the  parasites 
of  the  blood  of  the  rat  in  India.  After  that  followed  the  dicovery  of 
other  important  paihogenic  trypanosomes,  e.g.  in  1880  Evans  discovered 
the  trypanosome  causing  surra  in  horses  ;  in  1897  Bruce  found  the  try- 
panosome of  nagana,  known  as  the  tsetse  fly  disease.  In  1901  Dutton 
found  trypanosomes  in  human  blood,  and  in  1903  Castellani  found  them 
in  the  cerebrospinal  fluid  of  negroes  in  Uganda  suffering  from  sleeping 
sickness.  The  trypanosomes  found  by  Castellani  were  supposed  to 
be  a  different  species  from  that  of  Dutton  {Trypanosoma  gambiense) 
and  were  called  T.  ugandense  Castellani,  1903.  Kruse  later  gave  to  this 
trypanosome  the  name  T.castellanii  Kruse.  The  important  discoveries 
of  Dutton  and  Castellani  were  confirmed  by  D.  Bruce,  who  found  these 
trypanosomes  38  times  out  of  38  in  the  cerebrospinal  fluid  obtained  by 
a  lumbar  puncture  in  natives  of  Uganda  suffering  from  sleeping 
sickness,  and  twelve  times  out  of  thirteen  in  the  blood.  According  to 
the  rules  of  priority  applied  to  nomenclature,  the  last  two  specific  names 
must  give  way  to  Trypanosoma  gambiense  Dutton,  the  older  term. 

African  Sleeping  Sickness.  —  The  most  important  tsetse  fly  dis- 
ease is  African  sleeping  sickness,  the  causative  organism  of  which  is 
Trypanosoma  gambiense  (Fig.  16).  This  disease  is  endemic  in  cer- 
tain regions  of  Africa,  particularly  the  French  Congo  and  the  Congo  Free 
State,  where  for  several  years  it  has  increased  in  territory  and  has 
caused  great  ravages.  It  has  been  estimated  that  between  1896  and 
1906  from  400,000  to  500,000  natives  perished  from  this  pestilence. 
Dutton  and  Todd  found  that  in  some  villages  from  30  per  cent  to  50  per 
cent  of  the  population  was  infected. 

Age  does  not  affect  the  distribution  of  the  malady,  since  children, 
as  young  as  eighteen  months  to  two  years,  have  been  known  to  be 
infected.     Sex  does  not  influence  the  disease.     Occupation  and  social 

1  Laveran,    A.,    et    Mesnil,    1904.     Trypanosomes    et    Trypanosomiasis. 
Paris,  xi  +  417  pp. 


BLOOD-SUCKING   MUSCIDS 


211 


position,  however,  do  show  a  marked  influence.     The  great  majority  of 
the  cases  observed  are  among  the  agricultural  and  lower  classes. 

The  seasons  seem  not  to  influence  the  advance  of  the  disease,  but 
because  of  the  long  period  of  incubation  or  of  latency  which  precedes 
the  usual  appearance  of  nervous  symptoms,  the  influence  of  the  seasons 
is  hard  to  determine. 

There  are  two  distinct  phases  in  sleeping  sickness.  During  the 
first  phase  the  trypanosomes  are  in  the  blood  (Fig.  140),  usually  in  small 
numbers.  With  the  negroes  there  are  said  to  be  no  morbid  symptoms, 
but  with  the  whites  it  is  manifested  by  an  irregular  fever.  Glandular 
enlargement  is  an  early  and  constant  feature,  and  the  trypanosomes  are 
practically  always  found  in 
the  enlarged  glands.  In  the 
second  place,  the  trypano- 
somes are  constantly  found 
in  the  cerebrospinal  fluid ; 
there  is  nervousness  and 
trembling  until  drowsiness 
appears,  the  fever  taking  on 
the  hectic  character.  Drow- 
siness gives  way  to  lethargy, 
and  finally  the  victim  falls 
into  a  comatose  state. 

The  first  stage  may  last 
several  years,  while  the 
second  is  from  four  to  eight 
months'  duration,  exception- 
ably  one  year. 

The  description  of  the 
trypanosome  is  given  by 
Stephens  and  Christophers, 
viz.:  "12-28  by  1.5-3  micra. 
The  blepharoplast  is  oval.  There  is  not  uncommonly  a  vacuole  in 
close  association  with  it.  The  trypanosome,  at  least  in  animals,  oc- 
curs in  two  main  forms,  a  long  and  a  short."  Glossina  jyalpalis,  a 
tsetse  fly,  and  its  varieties,  is  unquestionably  the  principal,  if  not  the 
sole,  agent  of  transmission.  After  inoculation  into  the  human  the 
incubation  period  varies,  it  is  said,  from  several  months  to  several  years. 

A  second  species  of  trypanosome  producing  African  sleeping  sickness 
in  Rhodesia,  Nyasaland  and  adjoining  territory  is  T.  rhodesiense  (Ste- 
phens and  Fantham) }  In  this  trypanosome  the  nucleus  is  usually  in  the 
blepharoplast  end  of  the  parasite.     The  carrier  is  Glossina  morsitans. 


Fig.  140.  — ■  Photomicrograph  of  a  blood  smear, 
showing  Trypanosoma  gambiense  of  African  sleep- 
ing sickness.       X  625. 


1  Stephens,  J.  W.  W.,  and  Fantham,  H.  B.,  1913.  Trypanosoma  rhode- 
siense (Stephens  and  Fantham),  a  second  species  of  African  trypanosome  pro- 
ducing Sleeping  Sickness  in  man.  Trans.  Fifteenth  Internat.  Cong.  Hyg.  and 
Dem.,  Vol.  5,  Pt.  II,  pp.  615-619. 


212       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

Transmission.  • —  The  natives  of  French  Guinea  long  attributed  the 
power  of  disseminating  sleeping  sickness  to  flies  and  it  had  already 
been  shown  that  nagana,  a  disease  of  horses  and  dogs,  was  transmitted 
by  tsetse  flies  when  Button  and  Todd  studied  the  biting  flies  of  Gam- 
biense.  These  investigators  found  that  of  the  flies  which  bite  man  and 
animals,  Tahanus  dorsovittata  and  Glossina  palpalis  were  the  most  impor- 
tant, the  latter  being  very  common  in  western  Africa,  where  it  abounds  in 
the  mangroves  which  line  the  rivers  and  water  banks  during  the  warmer 
months  when  these  insects  are  very  troublesome.  Experiments,  how- 
ever, made  by  these  workers  gave  negative  results.  It  was  Bruce  and 
his  collaborators  who  subsequently  went  over  the  matter  and  showed 
that  Glossina  paljMlis  is  the  principal  agent  of  transmission.  Other 
tsetse  flies  known  to  transmit  sleeping  sickness  are  67.  palpalis  var. 
ivellmani,  Gl.  fusca,  also  67.  m.orsitans. 

Animal  experimentation  indicates  that  these  flies  can  transmit  the 
causative  protozoon  mechanically  for  a  period  of  less  than  forty-eight 
hours,  though  the  organisms  become  more  and  more  attenuated  after 
the  fly  has  bitten  the  diseased  individual  and  loses  its  power  of  infection 
in  less  than  forty-eight  hours.  Thus  the  tsetse  fly  proves  itself  a  me- 
chanical carrier  for  only  a  few  hours  during  which  time  its  soiled  proboscis 
is  involved,  i.e.  trypanosomes  are  injected  into  the  wound  produced  by 
the  bite  before  the  proboscis  is  cleaned. 

It  is,  however,  well  known  that  trypanosomes  taken  into  the  stomach 
of  the  fly  pass  through  a  metamorphosis,  developing  into  two  forms 
known  as  male  and  female.  These  latter  give  way  to  an  indift'erent  type 
and  in  from  four  to  five  days  all  trypanosomes  disappear.  Recent 
experimental  evidence  indicates  that  the  flies  become  infective  once 
more  at  the  end  of  about  four  weeks,  and  then  appear  in  the  salivary 
glands  of  the  insects.  Nuttall  ^  states  that  the  trypanosomes  appear 
in  the  salivary  glands  of  the  fly  after  a  period  of  twenty-five  to  twenty- 
eight  days  following  the  infective  meal.  During  this  interval,  except 
as  noted  above,  the  flies  are  incapable  of  producing  infection.  The 
parasites  in  the  salivary  glands  of  the  fly  resemble  T.  gamhieuse  as  seen 
in  the  mammalian  blood  and  they  persist  as  long  as  the  fly  lives. 
The  Sleeping  Sickness  Commission  has  found  that  infectivity  lasts  at 
least  ninety-six  days.  The  life  of  a  female  67.  palpalis  in  captivity  has 
been  observed  to  be  about  four  and  one  half  months.  The  same  author 
(Nuttall)  states  that  injections  of  either  the  gut  content  or  salivary  gland 
emulsion  produce  infection  after  about  the  twenty-fifth  day.  Under 
laboratory  conditions  only  about  5  per  cent  or  6  per  cent  of  the  flies 
become  infective. 

The  Question  of  Reservoirs.  —  Inasmuch  as  infective  flies  have 
been  taken  in  regions  uninhabited  by  man  for  at  least  three  years,  there 
must  be  some  other  animal  or  animals  in  which  the  trypanosome  of 

1  Nuttall,  G.  H.  F.  The  Herter  Lectures :  II,  Trypanosomiasis,  Parasit- 
ology, Vol.  V,  No.  4,  pp.  275-288. 


BLOOD-SUCKING   MUSCIDS  213 

sleeping  sickness  is  preserved  in  an  infective  state.  This  seems  further 
more  imperative  since  no  evidence  is  at  hand  that  the  trypanosomes  are 
transmitted  from  the  parent  fly  to  the  offspring,  i.e.  hereditarily.  There 
is  now  sufficient  evidence  at  hand  to  prove  that  the  African  antelope 
serves  as  a  perfect  reservoir  for  the  trypanosome/  that  these  animals 
recover  from  the  experimental  infection  and  therefore  serve  as  "  chronic 
carriers."  Many  animal?  may  serve  as  reservoirs.  (See  Nuttall, 
1913,  loc.  cit.) 

Nagana.  —  As  sleeping  sickness  is  to  man  so  is  nagana  to  domesti- 
cated animals,  especially  horses  and  dogs.  Tryyanosoma  brucei  Plimm 
and  Bradf .  is  the  causative  organism  of  nagana,  which  malady  was  early 
known  as  the  fatal  tsetse  fly  disease  of  African  horses  and  mules,  less 
fatal  in  cattle  and  sheep.  The  disease  is  characterized  by  progressive 
emaciation,  fever,  oedema  of  the  abdomen  and  genitalia  and  marked 
depression.  The  trypanosomes  are  found  in  the  blood  and  especially 
the  lymph  gland  swellings  from  the  beginning  of  the  first  symptoms. 

The  trypanosome  is  described  by  Stephens  and  Christophers,  viz. : 
"  26-27  micra  in  rats,  28-3o  micra  in  horses.  The  nucleus  lies  almost 
in  the  middle.  The  blepharoplast  is  almost  quite  round.  The  flagel- 
lum  is  generally  separated  from  it  by  a  slight  interspace." 

For  some  years  nagana  was  known  as  the  tsetse  fly  disease.  Glos- 
sina  morsitans  and  67.  longvpalpus  relate  to  its  transmission  in  practi- 
cally the  same  way  as  does  Glossina  jMlpalis  to  sleeping  sickness,  i.e. 
the  fly  is  infective  for  three  or  four  days  after  feeding  on  an  infected 
animal,  then  becomes  non-infective  for  a  period  of  about  three  weeks  and 
then  again  becomes  infective,  remaining  so  for  the  rest  of  its  life.  The 
incubation  period  after  inoculation  into  the  body  of  the  host  is  said  to 
be  about  ten  days. 

Control  of  the  Tsetse  Fly  Disease.  —  Thus  far  little  progress  has 
been  made  in  the  treatment  or  immunology  of  tsetse  fly  diseases ;  upon 
the  latter  no  doubt  rests  the  ultimate  solution  of  the  problem.  A  ready 
means  for  the  destruction  of  the  flies  is  unknown.  Although  numerous 
flies  may  be  destroyed  by  catching  them  with  sticky  substances  such 
as  birdlime,  their  reduction  is  hardly  if  at  all  noticeable.  Repellents, 
though  many  have  been  tried,  give  poor  results ;  oil  of  citronella  seems 
to  be  of  some  value.  The  general  and  practical  control  of  breeding 
places  oft'ers  unsurmountable  difficulties  owing  to  the  fact  that  the 
larvae  are  retained  within  the  body  of  the  female,  hence  are  not  directly 
dependent  upon  an  external  supply  of  food.  Starving  the  adult  flies  by 
eliminating  wild  animals  upon  which  they  are  dependent  for  blood  is  a 
method  employed  experimentally  in  many  localities.  The  wide  range 
of  food  animals,  the  question  of  reservoirs  and  the  need  of  domesticated 
animals  reduces  this  method  to  one  of  secondary  importance  to  be  em- 
ployed in  association  with  other  methods. 

A  study  of  the  habits  of  the  tsetse  shows  that  villages  located  in 
1  See  Proe.  Roy.  Soc,  Series  B,  vol.  83,  pp.  513-527,  1911. 


214       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

the  midst  of  extensive  clearings  and  not  too  near  water  courses  are 
largely  free  from  these  insects.  The  clearings  should  be  from  400  to 
600  yards  in  width  and  can  best  be  maintained  by  placing  them  under 
cultivation  (rice  and  larger  shade-producing  vegetation  excepted). 
Wells  should  be  utilized  for  water  supply. 

Screening  is  an  important  adjunct  to  the  control  of  sleeping  sickness. 
Dwellings,  trains,  steamers  and  other  conveyances  should  be  carefully 
screened. 

The  use  of  veils,  gloves  and  loose  white  garments  is  highly  recom- 
mended. 

Since  the  tsetse  fly  diseases  spread  along  trade  routes  and  extend 
from  infected  centers,  there  is  an  obvious  demand  for  the  control  of 
transportation  to  prevent  as  far  as  possible  the  employ  of  infected 
individuals. 

Owing  to  the  complicated  colonial  situation  in  Africa,  both  geo- 
graphically and  commercially,  the  control  of  trypanosomiasis  calls  for 
hearty  cooperation  among  the  powers  concerned. 

Systematic.  —  All  flies  belonging  to  the  genus  Glossina  partake 
of  the  following  characteristics :  medium-sized  flies  from  size  of  house 
fly  to  blowfly,  dark  brownish  in  color ;  wings  when  at  rest  folded  scissors- 
like  over  the  back,  longer  than  the  abdomen ;  fourth  longitudinal  vein 
bends  sharply  before  meeting  the  anterior  transverse  vein;  proboscis 
when  at  rest  projecting  horizontally  in  front  of  the  head ;  the  base  of 
proboscis  is  provided  with  an  onion-shaped  bulbous  expansion;  the 
arista  is  plumed  on  upper  side. 

The  following  species  ^  may  be  mentioned : 

(1)  Glossina  yalpalis  Robineau-Desvoidy  is  a  medium-sized  tsetse 
fly  from  8  to  9  mm.  in  length.  Its  general  color  is  light  brown  with 
a  dusting  of  gray.  The  antennae  are  dusky,  the  arista  has  18  aristal 
hairs.  The  thorax  heavily  dusted  with  gray  and  has  dark  lines  and 
spots.  The  abdomen  is  light  brown  beneath  dusted  with  gray; 
above  it  is  nearly  black  with  a  longitudinal,  median  narrow  light  brow^n 
stripe.  The  halteres  are  white.  The  legs  are  light  brown  with  indistinct 
dark  spots  on  the  tarsi.     The  hind  tarsi  are  black. 

This  species  is  found  throughout  West  Africa  from  the  Congo  to  the 
Senegal,  wherever  there  is  water. 

Glossina  palpalis  var.  ivellmani  Austin  varies  from  the  above  in  that 
it  has  a  yellowish  brown  frontal  stripe,  and  tarsi  nearly  white.  It  occurs 
in  Angola. 

Glossina  morsitans  Westw.  is  said  to  be  almost  identical  with  Glossina 
longipalpus,  except  that  it  is  ordinarily  somewhat  smaller.  Griinberg  ^ 
declares  that  it  would  be  more  correct  to  consider  morsitans  as  a  variety 
of  longipalpus.     Furthermore,  because  of  the  fact  that  both  species  are 

1  Griinberg,  Karl,  1907.  Die  Blutsaugenden  Dipteren.  Verlag  von  Gus- 
tav  Fischer  in  Jena,  vi  +  188  pp.,  127  figures.  (The  above  descriptions  of 
tsetse  flies  are  adapted  after  this  author.) 


BLOOD-SUCKING   MUSCIDS 


215 


transmitters  of  nagana,  the  separation  of  the  two  species  has  no  practical 
value. 

The  distribution  of  this  species  coincides  with  that  of  Gl.  longipalpus, 
though  it  is  ordinarily  attributed  to  a  much  greater  portion  of  Africa, 
because  its  habitat  consists  of  less  heavily  wooded  and  drier  areas. 

Glossina  longipalpus  Wiedem.  is  also  a  medium-sized  fly  ranging  from 
8-10  mm.  in  length.  The  color  is  light  brown  with  very  little  gray. 
The  antennae  are  dark  brown,  the  arista  is  light  brown  with  25  aristal 
hairs.  The  palpi  are  light  brown,  tipped  with  black.  The  thorax  is 
heavily  dusted  with  gray.  The  abdomen  is  light  brown,  marked  dor- 
sally,  to  the  right  and  left,  on  the  2-6  segments  with  black  semilunar 
lateral  spots,  resting  broadly  on  the  proximal  end  of  each  segment. 
The  halteres  are  white.  The  legs  are  light  brown  with  black  tipped 
pro-  and  meso-thoracic  tarsi ;  the  hind  legs  are  black. 

This  species  occurs  in  Sierra  Leone  and  British  Central  Africa. 

Other  species  of  Glossina  flies  are  the  following :  GL  pallicera  with 
20-22  aristal  hairs  (Griinberg) ;  Gl.  pallidipes  with  25  aristal  hairs 
(Griinberg) ;  GL  longipennis  with  18-20  aristal  hairs  (Griinberg) ; 
and  GLfusca,  a  large  species  (11-13  mm.)  also  with  18-20  aristal  hairs 
(Griinberg) . 

B.    Stomoxys  or  Stable  Flies 

Family  Muscidoe,  Genus  Stomoxys 

General  Characteristics.  —  Owing  to  similarity  in  color  and  size 
(Fig.  141)  the  Stomoxys  fly  is  often  mistaken  for  the  common  house  fly, 


Fig.   141.  —  (a)  The  common  house  fly  (Musca  domestica) ;    (6)  the  stable  fly  (Stomoxys 

calcitrans).      X  2.5. 


Musca  domestica.  However,  the  former  is  more  robust  with  broader 
abdomen.  In  color  it  is  brownish  gray  with  a  greenish  yellow  sheen ; 
the  outer  of  the  four  longitudinal  thoracic  stripes  are  broken  and  the 


216       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

abdomen  is  more  or  less  checkered.  The  wings  when  at  rest  are  widely 
spread  apart  at  the  tips,  are  distinctly  iridescent  and  the  apical  cell  is 
open.  When  resting  the  fly  has  its  head  thrown  well  up  and  the  wings 
slope  decidedly  toward  the  surface  upon  which  it  has  settled.  The 
proboscis  protrudes  bayonet-like  in  front  of  the  head.  The  antennal 
arista,  unlike  the  house  fly,  bear  setae  on  the  upper  side  only  (Fig.  29) . 

Habits.  —  Although  the  Stomoxys  fly  is  commonly  called  the  stable 
fly,  it  occurs  much  less  abundantly  (often  absent)  about  stables  than  does 
the  house  fly.  "Biting  house  fly  "  is  a  term  often  applied,  since  the  fly 
commonly  occurs  indoors  especially  in  the  autumn  and  during  rainy 
weather.  The  Stomoxys  fly  is  typically  an  out-of-door  fly  and  is  usually 
to  be  found  in  summer  where  domesticated  animals  occur,  especially 
cattle.  Its  occurrence  around  stables  is  traceable  to  the  presence  of 
cattle  or  horses  usually,  and  not  to  the  presence  of  manures  directly. 
Sunny  fences,  walls,  light-colored  canvas  coverings  and  light  objects  in 
general  when  in  the  proximity  of  cattle  are  abundantly  frequented  by 
Stomoxys  flies. 

The  Stomoxys  fly  is  a  vicious  "  biter,"  draws  blood  quickly  and 
fills  up  to  full  capacity  in  from  3  to  4  minutes  if  undisturbed,  but  ordi- 
narily even  when  undisturbed  changes  position  frequently  or  flies  to 
another  animal,  where  the  meal  is  continued.  This  fly  feeds  readily  on 
many  species  of  warm-blooded  animals,  for  example,  rats,  guinea  pigs, 
rabbits,  monkeys,  cattle,  horses  and  man.  Both  sexes  are  blood-suck- 
ing.    The  flight  of  the  Stomoxys  fly  is  direct  and  swift. 

Light  Reactions.  —  The  Stomoxys  flies  respond  positively  and 
strongly  to  light,  being  much  more  responsive  to  this  stimulus  than 
house  flies,  hence  the  former  are  normally  out-of-door  flies,  while  the 
latter  are  house  flies,  responding  readily  to  odors  emanating  from  the 
house.  Because  of  the  strong  positive  reaction  to  light  these  flies  can 
easily  be  transferred  from  breeding  jars  to  other  receptacles  by  covering 
the  former  w^ith  black  cloth,  leaving  an  opening  toward  the  light  into 
which  opening  a  test  tube  is  inserted.  Hundreds  of  flies  can  thus  easily 
be  transferred  in  a  few  minutes.  Observations  on  the  photic  reactions 
of  these  flies  bid  fair  to  give  very  interesting  results. 

The  larvae,  like  those  of  flesh  flies  and  house  flies,  are  decidedly  nega- 
tive to  light.  In  breeding  these  flies,  the  larvae  must  be  supplied  with 
sufficient  material  so  that  they  can  bury  themselves  deeply,  —  they  are 
thus  protected  against  light,  and  enough  moisture  must  be  applied  to 
keep  the  mass  of  material  in  a  "  soggy  "  condition.  Too  much  mois- 
ture is,  however,  destructive. 

Breeding  Habits  and  Life  History.  —  Although  the  Stomoxys  fly 
can  successfully  be  reared  in  the  manures  of  horses,  cattle,  sheep,  etc., 
it  may  be  safely  said  that  it  does  not  breed  commonly  in  excrement  under 
field  conditions  unless  straw  or  hay  predominates.  For  every  thousand 
house  flies  bred  in  horse  manure,  there  are,  as  a  rule,  not  more  than  one 
or  two  Stomoxys  flies.     The  very  best  breeding  places  are  afforded  by 


BLOOD-SUCKING  MUSCIDS 


217 


the  left-over  hay,  alfalfa  or  grain,  in  the  bottoms  or  underneath  out-of- 
Hnnr  feed  troughs  in  connection  with  dairies  (Fig.  142).     This  material 


Fig  142  —A  feed  trough  for  dairy  cattle  which  furnishes  an  ideal  breeding  Place  f or 
Stomoxyf  flies  The  moist  lower  layers  of  material  in  the  trough  furnish  abundant 
food  for  the  larvae. 

soon  becomes  soggy  and  ferments,  and  here  practically  pure  cultures  of 
Stomoxys  larv«  may  be  procured.     The  material  must  be  moist ;   dry- 


FiG.  143.  —  Showing    posterior  larval   spiracles  of  Stutuoxy^  calcitrans  (left) ;    Musca 
domestica  (vight).       X  21. 

ness  prevents  development.     Piles  of  wet  fermenting  weeds  and  lawn 
cuttings  also  furnish  fairly  good  breeding  material.     Piles  of -decaying 


218       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

onions  have  been  found  by  the  writer  to  harbor  myriads  of  larvae  late 
in  autumn. 

The  larvse  of  Stomoxys  and  of  the  house  fly  can  readily  be  differen- 
tiated by  the  form,  size  and  position  of  the  posterior  spiracles  (Fig.  143), 
otherwise  they  resemble  each  other  closely.  The  pair  of  posterior  spir- 
acles of  the  Stomoxys  larva  are  roughly  triangular,  widely  separated  and 
situated  near  the  periphery,  while  in  the  house  fl}^  larva  they  are  ellip- 
tical, quite  large,  close  together  and  more  central  in  position. 

The  eggs  of  the  Stomoxys  fly  are  about  1  mm.  long,  curved  on  one 
side,  straight  and  grooved  on  the  opposite  side.  In  depositing  her  eggs 
the  female  fly  often  crawls  far  into  the  loose  material,  depositing  her 
eggs  usually  in  little  pockets  in  small  numbers,  often  in  pairs.  Egg 
depositions  range  in  number  from  23  to  102,  usually  between  25  and 
50,  and  there  are  ordinarily  four  or  five  layings.  Mitzmain  ^  has 
found  in  his  observations  made  in  the  Philippine  Islands  that  the  maxi- 
mum number  of  eggs  produced  by  a  single  Stomoxys  is  632  and  possibly 
820,  and  that  there  may  be  as  many  as  twenty  depositions  during  the 
lifetime  of  the  female. 

The  incubation  period  varies  from  two  to  five  days,  commonly  three 
days,  at  a  temperature  of  26°  C.  Higher  temperatures  result  in  a  shorter 
incubation  period.  The  newly  hatched  larvse  bury  themselves  in  their 
food  at  once,  thus  protecting  themselves  against  light  and  dryness.  At 
a  temperature  of  from  21°  to  26°  C.  the  larvse  reach  full  growth  in  from 
fourteen  to  twenty-six  days.  Mitzmain  {loc.  cit.)  found  that  the  larval 
stage  averaged  twelve  days  at  a  room  temperature  of  30°  to  31°  C. 

Before  pupation  the  larvse  usually  crawl  into  the  drier  layers  of  the 
breeding  material,  where  the  chestnut-colored  pupse  are  often  found  in 
enormous  numbers.  The  pupse  are  from  6  to  7  mm.  long  and  may  be  rec- 
ognized by  the  posterior  spiracles  as  in  the  larva.  The  pupal  period  again 
varies,  dependent  on  temperature  especially.  At  a  temperature  of  from 
21°  to  26°  C.  this  period  varies  from  six  to  twenty-six  days,  with  the 
greatest  frequency  between  nine  days  and  thirteen  days  (Table  XII). 

TABLE  XII 

Table  Showing  Day  of  Emergence  of  Stomoxys  Calcitrans  after  Day 
OF  Pupation.  Larv^  Pupating  in  an  Insectary  at  a  Temperature 
OF  FROM  21°  to  26°  C. 


Pupal 

Period  in 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

Totals 

DATS 

A 

No.  flies 

1 

2 

42 

108 

424 

167 

85 

15 

8 

4 

2 

0 

858 

B 

No.  flies 

3 

10 

12 

80 

200 

70 

20 

16 

10 

19 

4 

3 

0 

427 

C 

No.  flies 

20 

125 

85 

100 

200 

70 

120 

50 

75 

30 

20 

30 

40 

15 

4 

0 

887 

1  Mitzmain,  M.  B. 
a  preliminary  account. 
Sec.  B.,  pp.  29^8. 


1913.     The  bionomics  of  Stomoxys  calcitrans  Linnaeus; 
The  Philippine  Journal  of  Science,  Vol.  VIII,  No.  1, 


BLOOD-SUCKING  MUSCIDS  219 

At  an  average  temperature  of  29°  C.  Mitzmain  {loc.  cit.)  found  the 
pupal  period  to  average  fi^'e  days. 

If  not  handicapped,  the  imago  emerges  with  astonishing  rapidity, 
crawls  away,  unfolds  its  wings  and  is  ready  to  fly  away  in  less  than  half 
an  hour.  The  fact  that  the  proboscis  is  temporarily  attached  beneath 
the  thorax  gives  the  newly  emerged  insect  a  very  peculiar  appearance, 
and  it  may  then  be  easily  mistaken  for  a  house  fly. 

Summarizing  the  life  history  of  the  Stomoxys  fly  (Fig.  144)  it  may  be 
said  that  at  a  temperature  of  21°  to  26°  the  shortest  periods  are :  egg, 
two  days,  larva,  fourteen  days,  pupa,  six  days,  total  twenty-two  days; 
the  average,  egg,  three  days,  larva,  fifteen  days,  pupa,  ten  days,  total, 
twenty-eight  days ;  the  maximum,  egg,  five  days,  larva,  twenty-six  days, 
pupa,  twenty-six  days,  total,  fifty-seven  days.     The  total  time  at  21° 


£^fs  Larva  /^^upa  y^duit 

A/of  to  J  a  me  jica/e 


Fig.  144.  —  Showing  the  life  history  of  the  stable  tiy  or  stomoxys  fly  (Sto>7ioxys  calcitrans). 
(Photo  by  H.  F.  Gray.)      X  2. 

from  the  laying  of  the  egg  to  the  emergence  of  the  imagines  was  from 
thirty-three  days  to  thirty-six  days  as  observed  in  five  individual  cases. 
Mitzmain  {loc.  cit.)  reports  the  development  of  this  fly  in  twelve  days 
under  optimum  conditions. 

Copulation  takes  place  within  a  week  and  egg  deposition  begins  in 
about  eighteen  days  after  emergence  from  the  pupa  cases  at  a  temper- 
ature of  from  21°  to  26°  C.  Higher  temperatures  undoubtedly  decrease 
this  time. 

Longevity.  —  With  approximately  4000  flies  under  continuous  daily 
observation  in  glass  quart  jars,  50  flies  to  a  set,  the  writer  has  found  that 
the  average  length  of  life  of  the  Stomoxys  fly  under  favorable  condi- 
tions of  feeding  {i.e.  daily  feedings  on  monkeys  or  rabbits)  is  about 
twenty  days.  The  maximum  life  under  these  conditions  was  found  to 
be  sixty-nine  days  and  several  hours,  —  observed  in  a  female  (Fig.  145) . 

Mitzmain  {loc.  cit.)  has  found  the  maximum  for  a  female  fly  to  be 
seventy-two  days  and  for  the  male  ninety-four  days. 

The  writer  has  observed  that  a  set  of  flies  which  fed  only  on  sugar 
water  deposited  no  eggs,  although  many  of  them  lived  twenty  days  or 


220       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


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BLOOD-SUCKING   MUSCIDS  221 

longer,  while  control  flies  fed  on  blood  did  lay  eggs.  Hence  it  seems 
apparent  that  the  flies  must  have  blood  in  order  to  develop  eggs. 

As  a  Cattle  Pest.  —  In  a  most  useful  and  interesting  paper  on  the 
stable  fly,  as  a  live  stock  pest,  Bishopp  ^  regards  this  fly  as  very  impor- 
tant. Injury  is  brought  about  in  various  ways,  e.g.  worry,  due  to  the 
attacks  of  myriads  of  flies ;  loss  of  blood  ;  lessening  of  the  milk  supply 
from  40  to  60  per  cent ;  loss  of  flesh ;  bringing  on  attacks  of  acute 
Texas  fever  if  the  cattle  are  already  parasitized  ;  etc. 

Surra.  —  Surra  is  one  of  the  most  important  diseases  of  horses  in 
the  Philippine  Islands,  and  its  spread  on  these  islands  behooves  the 
government  to  a  most  careful  consideration  of  its  transmission.  The 
causative  organism  is  Trypanosoma  evansi  (see  Chapter  XII)  which  is 
harbored  by  a  number  of  hosts,  mainly  horses,  in  which  the  disease  is 
highly  fatal,  also  mules  and  the  carabao,  and  experimentally  in  monkeys, 
guinea  pigs  and  rabbits. 

The  Stomoxys  fly  has  been  regarded  by  some  authors  as  an  impor- 
tant carrier  of  this  trypanosome.  Unfortunately  there  is  little  or  no 
conclusive  experimental  evidence  in  favor  of  this  theory.  Mitzmain  ^ 
in  a  most  important  contribution  on  this  subject  presents  very  good  evi- 
dence that  this  fly  need  not  be  regarded  as  a  factor  in  the  transmission 
of  surra,  that  its  spread  is  attributable  mainly  to  a  horsefly,  Tabanus 
striatus,  the  common  horsefly  of  the  Philippine  Islands.  In  a  letter  to 
the  writer  Mitzmain  states  that  Stomoxys  calcitrans  was  used  daily  on 
clean  animals  up  to  ninety-four  days  after  removal  from  the  infected 
hosts  without  successful  transmission. 

Poliomyelitis.  —  Poliomyelitis,  also  known  as  infantile  paralysis, 
was  first  described  in  1820  in  Norway,  and  it  seems  quite  likely  that  the 
spread  of  this  disease  is  traceable  to  immigrants  from  the  Scandinavian 
peninsula.  Severe  epidemics  of  this  disease  are  apparently  not  recorded 
until  recent  years,  the  latter  few  years  of  the  last  century  and  the 
beginning  of  this. 

Apparently  the  first  epidemic  to  be  reported  in  the  United  States 
was  in  1894  in  Vermont,  and  a  year  later  a  small  epidemic  was  reported 
in  California.  During  the  past  five  years  the  disease  has  been  spreading 
to  an  alarming  extent.  In  1907  over  2500  cases  occurred  in  New  York 
State,  in  1909  nearly  1000  cases  in  Massachusetts  and  over  600  cases  in 
Nebraska;  in  California  for  the  year  beginning  November  1,  1911,  and 
ending  October  31,  1912,  there  were  495  cases  with  a  mortality  of  23.3 
per  cent.  Children  between  the  ages  of  three  and  four  seem  to  be  most 
susceptible  to  the  disease  and  the  mortality  is  highest  between  these 
ages.  The  disease  is,  however,  not  restricted  to  infants,  since  adults 
are  known  to  show  characteristic  symptoms. 

The  symptoms  of  the  disease  in  the  first  stage  are  vague,  —  there  is 

^  Bishopp,  F.  C,  1913.     The  stable  fly  (Stomoxys  calcitrans  L.),  an  important 
live  stock  pest.     Journ.  Econ.  Ento.,  Vol.  6,  No.  1,  pp.  112-127. 
2  Mitzmain,  M.  B.,  1913  (loc.  cit.). 


222       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

fever,  nervousness,  gastric  and  intestinal  disturbances,  loss  of  appetite 
and  headache ;  these  symptoms  are  followed  by  the  more  definite  condi- 
tions of  paralysis  of  arms  and  legs,  usually  asymmetrical,  trembling  and 
finally  complete  paralysis.  Death  often  occurs  through  paralysis  of  the 
diaphragmatic  muscles.  If  recovery  takes  place,  often  months  elapse 
before  complete  use  of  arms  and  legs  is  regained. 

The  causative  organism  is  unknown,  but  is  filterable  and  hence 
belongs  to  that  already  large  group  of  ultra-microscopic  organisms, 
including  those  of  yellow  fever  and  dengue.  The  incubation  period  in 
the  human  has  not  been  ascertained,  but  in  monkeys  it  is  as  short  as 
three  or  four  days  and  in  these  animals  death  often  ensues  in  five  days. 

The  epidemiology  of  Poliomyelitis  is  complicated.  The  virus  is 
known  to  retain  its  virulence  under  most  adverse  conditions,  said  to 
remain  virulent  in  dust  (Neustaedter  and  Thro).^  The  disease  can 
be  produced  by  painting  the  nasal  mucosa  with  the  virus.  All  this 
would  seem  to  point  toward  ease  of  transmission  and  infection,  which 
is  really  not  the  case,  otherwise  epidemics  of  this  disease  in  schools  would 
be  common  occurrences.  Again,  healthy  monkeys  caged  with  monkeys 
infected  with  the  disease  do  not  readily  become  infected  by  contact. 
Notwithstanding  these  facts  cases  are  cited  in  which  the  disease  has 
been  transmitted  by  contact.  On  the  other  hand  cases  are  numerous 
in  which  the  patients  are  far  separated  from  other  cases. 

Because  of  this  peculiar  distribution  the  attention  of  investigators 
has  been  called  to  the  possibility  of  insect  transmission.  The  following 
quotation  is  taken  from  the  California  State  Board  of  Health  Special 
Bulletin  on  Poliomyelitis  (October  15,   1912). 

"In  1909,  Dr.  J.  H.  Hill,  Epidemiologist  of  the  Minnesota  State  Board  of 
Health,  presented  the  apparent  relation  of  dusts  to  the  occurrence  of  the  disease 
and  its  frequent  appearance  on  premises  having  accommodations  for  horses  and 
other  animals. 

"Professor  W.  B.  Herms,  of  the  University  of  California,  has  for  several 
years  considered  the  "biting  fly"  {Stomoxys  calcitrans)  to  be  a  possible  factor  in 
transmitting  the  disease. 

"Dr.  M.  W.  Richardson,  Secretary  Massachusetts  State  Board  of  Health,  in 
1911  was  one  of  the  first  workers  to  begin  the  systematic  collection  of  insects 
found  on  the  premises  of  poliomyelitis  cases.  His  observations  and  his  strong 
suspicion  of  the  "biting  fly"  based  upon  finding  this  species  of  fly  as  the  only 
insect  constantly  present  in  the  majority  of  houses  where  poliomyelitis  had 
occurred,  were  presented  to  the  American  Pubhc  Health  Association  in  Havana 
in  December,  1911. 

"Dr.  Flexner  of  the  Rockefeller  Institute  for  Medical  Research  and  his  as- 
sociates, in  their  several  progress  reports  on  Poliomyelitis  have  pointed  out 
the  possibility  of  insects  being  a  factor  in  disseminating  the  disease,  and  have 
emphasized  the  fact  that  if  this  could  be  proved  it  would  explain  many  of  the 
difficult  points  in  its  epidemiology. 

"Doctor  Frost  of  the  United  States  Public  Health  Service  has  been  con- 
stantly observing  the  epidemiological  factors  in  American  outbreaks  of  poliomy- 

1  Neustaedter,  M.,  and  Thro,  W.  C,  N.  Y.  Med.  Journ.,  1911,  XCIV, 
p.  813. 


BLOOD-SUCKING   MUSCIDS  223 

elitis  during  the  past  three  years,  in  an  effort  to  collect  evidence  supporting  or 
disproving  the  efficiency  of  administrative  measures  that  have  hitherto  pre- 
vailed. 

"In  the  summer  of  1912,  Dr.  Richardson  continued  his  work  and  Dr.  M.  J. 
Rosenau  of  Harvard  University  began  a  series  of  scientific  experiments  to 
demonstrate  if  possible,  whether  poliomyelitis  can  be  transferred  from  infected 
monkeys  to  well  monkeys  through  the  agency  of  the  "biting  fly"  {Stotnoxrjs 
calcitrans).  In  a  preliminary  scientific  announcement,  September  26,  1912, 
before  the  International  Hygienic  Congress,  Dr.  Rosenau  stated  that  he  had 
succeeded  in  accomplishing  this  in  his  first  series  of  experiments." 

The  following  is  quoted  from  a  report  of  Rosenau' s  work  in  the 
Journal  of  the  American  Medical  Association  (Vol.  LIX,  No.  14,  p.  1314) 
under  "  Proceedings  of  the  International  Congress  on  Hygiene  and 
Demography." 

"In  reference  to  the  transmission  of  poliomyelitis  by  the  biting  fly,  we  were 
led  to  focus  our  attention  on  this  biting  ^y  {Stomoxys  calcitrans)  as  an  inter- 
mediate host  in  the  transmission  of  a  particular  infection  referred  to  by  Dr. 
Richardson.  When  I  first  began  to  study  the  disease,  I  regarded  it  probably 
as  one  which  is  spread  by  direct  contagion,  by  contact,  either  directly  or  in- 
directly, from  person  to  person.  The  first  circumstance  which  shook  my  faith 
that  we  were  dealing  with  a  contagious  disease  was  the  fact  that  we  had  eighteen 
negative  results  in  attempting  to  prove  the  presence  of  the  virus  in  the  secretions 
from  the  nose  and  throat.  I  could  not  help  asking  at  the  time  if  it  were  not 
possible  to  find  the  virus,  which  is  so  potent,  in  the  secretions  of  the  nose  and 
throat  of  persons  who  have  the  disease  and  those  who  are  convalescing  from 
the  disease.  These  results  were  confirmed  at  the  same  time  by  Strauss,  of 
New  York,  who  had  negative  results  in  a  large  series  and  by  Neustaedter's 
recent  results  and  by  other  results,  all  of  the  examinations  having  proven  nega- 
tive excepting  one  recently  reported  by  Kline,  Patterson  and  his  associates  at 
this  congress  and  in  the  literature  recentl.y. 

"A  second  circumstance  which  led  me  to  believe  we  were  not  dealing  witha 
contagious  disease  was  the  fact  brought  out  by  Dr.  Richardson.  Children  in 
all  stages  of  this  disease  were  crowded  into  schools,  institutions,  tenement 
districts  and  other  places  where  there  was  every  chance  for  the  spread  of  the 
disease,  but  it  did  not  spread  there,  but  it  continued  to  spread  in  the  rural, 
thinly  scattered  districts  where  one  would  not  expect  to  find  contagious  disease. 
There  was  a  resemblance  to  rabies.  All  those  who  have  worked  with  this  virus 
in  laboratories  were  at  once  struck  with  the  resemblance  between  poliomyelitis 
and  rabies.  The  latter  being  a  wound  infection,  there  is  some  analogy  between 
it  and  poliomyelitis,  and  poliomyelitis  might  be  transmitted  through  some  sort 
of  wound.  I  was  fortunate  enough  to  have  had  experience  with  yellow  fever, 
both  in  the  investigation  of  it  and  the  sanitary  measures  against  it,  before  the 
mosquito  period,  and  I  was  much  struck  with  many  analogies  which  came  to  me 
between  that  disease  and  certain  features  of  poliomyelitis. 

"The  work  I  bring  to  your  attention  consisted  of  taking  a  number  of  flies,  — 
Stomoxys  calcitrans,  —  caught  in  a  net  and  bred  for  the  purpose  ;  you  can  catch 
several  hundred  of  these  flies  in  a  stable  in  a  very  short  time.  We  placed  these 
flies  in  a  large  cage  and  exposed  monke.vs  to  their  bites,  the  raonkej^s  having 
been  purposely  infected  with  the  virus  of  poliomyelitis.  Care  was  taken  to 
place  the  monkeys  in  the  cages  in  all  stages  of  the  disease,  before  and  after. 
In  fact  a  monkey  would  be  exposed  to  the  bites  of  the  flies  on  the  same  day  he 
was  infected,  so  that  the  flies  could  drink  the  blood  of  the  monkey  during  all 
stages  of  the  period  of  incubation  of  the  disease,  for  we  do  not  yet  know  in  what 


224       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

stage  of  the  infection  the  virus  appears  in  the  blood  at  its  nnaxinnuro,  or  the  best 
period  for  infecting  these  flies.  Following  this  we  exposed  healthy  n^onkeys  to 
the  bites  of  the  saniC  flies,  and  after  several  weeks'  time  these  healthy  monkeys 
came  down  with  a  disease  which  in  all  essential  respects  resen.hles  anterior 
poliomyelitis.  Out  of  twelve  healthj'  monkeys  so  exposed,  six  of  them  now  have 
symptoms  of  the  disease,  three  of  them  in  the  virulent  form.  Of  the  other  three 
monkeys,  tw^o  are  coming  dow*n,  but  one  seems  to  have  a  nikrer  infection  than 
the  other.  This  mild  infection  consists  of  trembling  and  weakness  of  the  hand, 
and  some  weakness  of  the  jaw  which  lasted  about  a  week  or  so  and  then  passed 
away.  We  cannot  be  sure  whether  that  is  true  poliorryelitis  or  not  until  we 
arc  able  to  test  the  monkey  subsequently.  If  it  were  poliomyelitis,  that  monkey 
will  be  'immune.'  In  three  of  the  six  cases  that  came  down  with  the  disease, 
having  been  bitten  by  flies,  there  was  some  diarrhea.  The  disease  in  the  n.onkey 
resembles  more  closely  that  which  we  see  in  children,  rather  than  the  disease  we 
produce  purposely  experimentalh'  by  bringing  the  virus  in  direct  association 
with  the  central  nervous  system.  Of  course,  that  may  be  onlj^  a  coincidence,  but 
it  is  interesting." 

The  work  of  Rosenau  Avas  repeated  and  confirmed  during  October, 
1912,  by  Anderson  and  Frost  ^  who  summarize  as  follows :  "  Three 
monkeys  exposed  daily  to  the  bite  of  several  hundred  Stomoxys,  wdiich 
at  the  same  time  were  allow^ed  daily  to  bite  two  intracerebrally  inocu- 
lated monkeys  developed  quite  typical  symptoms  of  poliomyelitis  eight, 
seven  and  nine  days  from  the  date  of  their  first  exposure." 

In  order  to  verify  the  findings  of  the  above  experiments  and  to 
secure  further  biological  evidence  if  possible  the  writer,  in  cooperation 
with  Dr.  W.  A.  Sawyer,^  undertook  a  special  investigation  of  the 
problem,  beginning  in  October,  1912.  Believing  it  unwdse  to  use  flies 
collected  out  of  doors  these  insects  were  reared  for  the  purpose  in  an 
insectary.  The  importance  of  this  precaution  is  made  evident  bj'  the 
fact  that  flies  captured  out  of  doors  in  Berkeley  wxre  shown  to  transmit 
a  pathogenic  organism  to  a  rabbit,  infection  undoubtedly  having  been 
acquired  in  nature.  This  infection  resulting  in  abscess  was  successfully 
transmitted  from  rabbit  to  rabbit  through  the  agency  of  the  Stomoxys 

fly. 

"In  Rosenau's  armouncement  he  stated  that  the  monkej^s  show'ed  symptoms 
of  poliomyelitis  several  weeks  after  tlie  flies,  which  were  biting  them  frequentl.y, 
had  had  their  first  opportunity  to  receive  infection  from  sick  monkeys.  This 
would  allow  abundant  time  for  a  definite  biological  change  in  the  virus,  prepar- 
ing it,  during  the  incubation  in  the  fly  as  intermediate  host,  for  successful 
inoculation  into  the  warm-blooded  monkey.  Such  a  process  seemed  not  an 
improbable  explanation  of  the  results  when  we  considered  that  Rosenau  was 
dealing  with  a  blood-sucking  insect  and  a  disease  in  which  the  blood  bad  been 
shown  to  have  very  low^  infectivity  on  direct  inoculation.  The  symptcns  of 
poliomyelitis  in  the  experunents  of  Anderson  and  Frost  appeared  so  scon  after 

1  Anderson,  John  F.,  and  Frost,  Wade  H.,  1912.  Transmission  of  polio- 
myelitis bv  means  of  the  stable  fly  (Stomoxys  calcitrans).  U.  S.  Pub.  Health 
Repts.,  Vol.  XXII,  No.  43,  Oct.  25,  1912. 

2  Sawyer,  W.  A.,  and  Herms,  W.  B.,  1913.  Attempts  to  transmit  polio- 
myelitis bv  means  of  the  stable  Ay  {Stomoxys  calcitrans).  Journ.  Amer.  Med. 
Assoc.,  Vol.  LXI,  pp.  461-466. 


BLOOD-SUCKING  MUSCIDS  £25 

the'first  possible  transference  of  infectious  material  that  in  all  probability  the 
process  consisted  of  a  mechanical  transference  of  blood  or  other  infectious 
material  taken  up  by  the  flies  while  repeatedly  piercing  the  skin.  The  extreme 
shortness  of  time  available,  in  their  experiments,  for  incubation  of  the  virus  in 
the  fly  is  apparent  when  we  consider  that,  in  the  interval  of  nine  or  ten  days, 
we  must  allow  also  for  the  development  of  the  virus  in  the  original  inoculated 
monkcj^s  and  for  the  incubation  period  in  the  monkeys  infected  by  the  flies." 
(Saw3^er  and  Henns,  loc.  cit.) 

Assuming  the  accuracy  of  the  work  of  Rosenau  and  Anderson  and 
Frost,  it  seemed  advisable  to  plan  the  experiments  so  as  to  secure,  if 
possible,  an  answer  sooner  or  later  to  each  of  the  following  questions  : 

1 .  Is  the  Stomoxys  fly  merely  a  mechanical  carrier  of  poliomyelitis  or  is  it  an 

intermediary  host  ? 

2.  If  it  is  an  intermediary  host  how  much  time  must  elapse  after  biting  before 

it  can  infect  another  animal  ? 

3.  How  long  does  the  fly  remain  infective? 

4.  How  soon  after  infection  does  the  experimental  animal  become  infective  to 

the  fly  and  how  long  does  the  animal  remain  infective  to  the  fly  ? 

5.  Does  the  severity  of  the  infection  increase  with  the  number  of  bites  of  the 

fly? 

6.  What  is  the  percentage  of  infected  flies  in  nature  ? 

7.  Do  other  biting  insects  carry  this  disease  ? 

8.  Can  other  animals  be  inoculated  by  the  Stomoxys  fly  and  serve  as  carriers 

or  receptacles  of  the  disease,  e.g.  chickens,  rabbits,  guinea  pigs,  rats,  mice, 
pigs,  dogs,  cats,  horses  and  cattle  ? 

9.  What  are  the  best  methods  to  exterminate  the  Stomoxys  fly? 

10.  What  precautions  are  necessary  to  prevent  the  existing  flies  from  coming 
in  contact  with  infectious  patients  and  carrying  the  disease  to  other 
individuals  ? 

A  series  of  seven  experiments  was  conducted  covering  a  period  of 
about  nine  months  and  involving  the  use  of  about  four  thousand  labora- 
tory reared  flies,  a  large  number  of  monkeys,  rabbits  and  other  rodents. 
The  experiments  were  carefully  planned  and  every  precaution  w^as  taken 
to  bring  about  accurate  results.  In  the  first  experiment  approximately 
1750  flies  were  used,  applying  these  to  the  animals  in  bobbinet-covered 
glass  jars  (quarts),  50  flies  to  a  set  (Fig.  146).  A  rhesus  monkey  was 
inoculated  intracerebrally  with  2  cc.  of  a  suspension  of  Flexner  virus, 
and  the  first  set  of  flies  was  placed  on  this  animal  immediately  after 
inoculation  and  after  ten  minutes'  feeding  transferred  to  a  healthy 
monkey.  The  next  day  new  sets  of  flies  were  used  and  again  trans- 
ferred to  the  same  monkey,  and  those  flies  which  had  bitten  the  sick 
monkey  on  the  previous  day  (24  hours  ago)  were  placed  to  bite  another 
unused  monkey.  In  this  way  new  flies  were  used  each  day  and,  trans- 
ferred immediately  to  the  first  healthy  monkey ;  thus  this  animal  al- 
ways received  flies  that  had  fed  for  the  first  time  on  the  sick  monkey  and 
transferred  immediately.  The  second  healthy  monkey  always  received 
flies  supposed  to  hold  infection  for  24  hours ;  the  third  animal,  flies  of 
48  hours  standing ;  the  fourth  animal,  flies  of  four  days ;  the  fifth  animal, 


226       MEDICAL   AND   VETERINARY   ENTOMOLOGY 


flies  of  nine  days ;  the  sixth  animal,  flies  of  seventeen  days ;  the  seventh, 
flies  of  thirty  days ;  and  the  eighth  received  daily  all  the  survivors  of 
the  entire  series  until  all  the  flies  were  dead. 

Between  monkey  feedings  until  the  last  animal  was  used,  the  flies 
were  kept  alive  by  allowing  them  to  feed  on  rabbits  every  other  day, 
a  new  rabbit  being  used  each  time.     The  rabbits  remained  healthy. 

In  the  above  experiment  all  the  monkeys  remained  healthy  except 
two ;  namely,  the  first  one  which  received  the  virus,  and  that  animal  died 
on  the  fourth  day  of  typical  poliomyelitis,  and  the  seventh  animal,  which 
died  of  acute  pneumonia. 

Except  in  cases  of  immediate  transfer  when  only  ten  minutes  of 
feeding  was  permitted,  the  flies  were  given  ample  opportunity  to  feed 


Fig.  146.  —  Showing  jar  method  of  feeding  Stomoxys  flies  on  monkeys.  The  jars  are 
covered  with  bobbinet  and  sealed  with  adhesive  plaster.  The  flies  thrust  their  probos- 
cides  through  the  meshes  and  thus  come  in  contact  with  the  monkey. 

until  satisfled  (normally  from  20  to  30  minutes)  and  ordinarily  the  flies 
fed  well. 

In  the  second  experiment  an  immobilized  inoculated  monkey  was 
placed  in  a  screened  fly  cage  (16"  X  28"  X  18")  with  500  Stomoxys 
flies.  This  animal  remained  in  the  cage  with  the  flies  for  two  hours, 
after  which  it  was  removed  and  a  healthy  monkey  substituted  (also 
immobilized).  The  second  animal  remained  in  the  cage  with  the 
flies  also  for  a  period  of  two  hours.  This  was  repeated  daily  until  the 
inoculated  monkey  died  of  poliomyelitis,  after  which  the  healthy  animal 
was  returned  to  the  cage  daily  until  all  the  flies  were  dead.  The  results 
proved  negative. 

In  the  third  experiment  the  flies  in  jars  as  before  to  the  number  of 
about  GOO  were  kept  continuously  under  higher  temperatures  in  the 


BLOOD-SUCKING   MUSCIDS  227 

insectary,  —  temperature  ranging  from  23°  to  26°  C.  The  flies  were 
applied  for  three  minutes  to  the  belly  and  chest  of  a  diseased  (poliomye- 
litis) monkey  and  then  three  minutes  to  the  belly,  chest  and  face  of  a 
healthy  monkey,  and  thus  exchanged  back  and  forth  at  three-minute 
intervals  until  all  flies  had  had  a  good  chance  to  feed  daily.  After  the 
death  of  the  diseased  monkey  the  flies  were  fed  daily  on  the  healthy 
monkey  until  all  the  flies  were  dead.     The  results  were  negative. 

In  the  next  experiment  a  fly  filtrate,  made  of  flies  which  had  one 
hour  previously  fed  on  a  monkey  at  the  height  of  the  disease,  was  inocu- 
lated, intracerebrally,  into  a  healthy  monkey  with  negative  results,  as 
also  did  a  filtrate  made  from  flies  having  fed  four  days  previously. 

In  the  fifth  experiment  large  numbers  of  flies  were  applied  daily  at 
three-minute  intervals  between  a  poliomyelitis  monkey  and  two  healthy 
monkeys  and  continued  daily  on  the  latter  after  the  diseased  monkey 
died.     The  results  were  negative  as  before. 

It  was  thought  that  possibly  the  results  of  the  previous  investigators 
had  been  due  to  the  access  of  the  flies  to  infectious  material  on  the  sur- 
faces of  the  diseased  monkeys  and  about  their  body  orifices,  hence  a 
parallel  experiment  to  the  one  above  cited  was  undertaken  with  the  differ- 
ence that  the  abdomen  and  chest  of  the  diseased  monkey  were  painted, 
before  the  fly  feedings,  with  a  mixture  of  his  saliva,  his  feces,  and  (late 
in  the  disease)  his  nasal  washings  in  physiological  salt  solution.  Even 
so  the  results  were  negative.  Later,  after  the  death  of  the  diseased 
monkey,  an  emulsion  of  the  highly  infectious  brain  tissue  was  used  in 
place  of  the  mixture  of  feces,  saliva  and  nasal  secretions.  The  brain  emul- 
sion was  painted  on  a  normal  monkey  after  which  flies  were  applied  and 
transferred  as  before  to  two  other  normal  monkeys,  all  remaining  well. 
Poliomyelitis  had  not  been  produced  in  a  well  monkey  by  stable  flies 
even  when  they  had  to  drive  their  proboscides  through  a  layer  of  highly 
infectious  brain  tissue  in  order  to  pierce  the  skin,  and  the  same  flies  did 
not  transmit  the  disease  on  subsequent  bitings  of  two  other  monkeys. 

Conclusions.  —  From  the  above-cited  experiments  the  following  con- 
clusions were  drawn : 

1.  In  a  series  of  seven  experiments  in  which  the  conditions  were 
varied  we  were  unable  to  transmit  poliomyelitis  from  monkey  to  monkey 
through  the  agency  of  the  stable  fly. 

2.  Further  experiments  may  reveal  conditions  under  which  the  stable 
fly  can  readily  transfer  poliomyelitis,  but  the  negative  results  of  our  work 
and  of  the  second  set  of  experiments  of  Anderson  and  Frost  ^  lead  us  to 
doubt  that  the  fly  is  the  usual  agent  in  spreading  the  disease  in  nature. 

3.  On  the  basis  of  the  evidence  now  at  hand  we  should  continue  to 
isolate  persons  sick  with  poliomyelitis  or  convalescent,  and  we  should 

1  Anderson,  John  F.,  and  Frost,  W.  H.,  1913.  Poliomyelitis :  Further 
attempts  to  transmit  the  disease  through  the  agency  of  the  stable  fly  (Stomoxys 
calcitrans).  U.  S.  Pub.  Health  Reports.  Washington,  May  2,  1913,  Vol. 
XXVIII,  pp.  833-837. 

Q 


228       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

attempt  to  limit  the  formation  of  human  carriers  and  to  detect  and 
control  them.  Screening  of  sick  rooms  against  the  stable  fly  and  other 
flying  insects  is  a  precaution  which  should  be  added  to  those  directed 
against  contact  infection,  but  not  substituted  for  them. 

4.  The  measures  used  in  suppressing  the  house  fly  are  not  appli- 
cable to  the  control  of  the  stable  fly  owing  to  its  dift'erent  breeding  habits 
and  food  supply. 

Control.  —  The  more  important  breeding  places  of  the  Stomoxys 
can  be  destroyed  by  removing  the  moist  feed  wastes  from  feeding 
troughs  and  from  stalls,  stables,  etc.,  and  scattering  this  material  so 
that  it  dries  out  quickly.  Considerable  moisture  is  necessary  for  the 
development  of  the  larvae,  therefore  dry  material  is  not  suitable. 
Weeds,  lawn  cuttings,  vegetables,  rubbish,  decaying  onions,  etc., 
must  not  be  permitted  to  accumulate  in  piles  long  enough  to  decay 
and  accumulate  moisture.  The  absence  of  stables  does  not  insure 
against  the  Stomoxys  fly  even  though  it  is  called  the  stable  fly.  The 
commonest  fly  around  stables  is  the  house  fly,  while  the  Stomoxys  may  be 
entirely  absent.  This  fly  is  near  stables  because  of  the  blood  of  horses, 
cattle,  etc.,  and  not  because  suitable  breeding  material  is  commonly 
found  there.  Open  country  without  stables  is  sometimes  over  ridden 
with  these  biting  flies. 

Bishopp  (loc.  cit.)  has  shown  that  straw  stacks  (oats  and  wheat) 
are  important  breeding  places  of  the  Stomoxys  fly,  hence  he  recommends 
"  that  the  straw  for  feeding  and  bedding  purposes  be  baled  and  stored 
under  cover.  Where  this  is  not  practicable  the  stacks  should  be  rounded 
up  so  as  to  make  the  top  largely  rain  proof  and  the  sides  nearly  vertical.'* 

Repellent  decoctions  on  domesticated  animals  only  give  temporary 
relief.  Bishopp  recommends  as  the  most  efficacious  "  a  mixture  of 
fish  oil,  oil  of  tar,  and  oil  of  pennyroyal  with  a  little  kerosene  added." 

Screening  barns  is  recommended  where  flies  are  abundant. 

Systematic.  — The  genus  Stomoxys  includes  about  ten  species,  of 
which  St.  calcitrans  Linn,  is  the  type,  also  the  best  known  and  most 
widely  distributed  species,  occurring  commonly  on  every  continent. 

Other  species,  all  occurring  in  smaller  numbers  in  restricted  localities 
in  Africa,  are :  St.  glauca  Griinb. ;  St.  inornata  Griinb.  and  St.  nigra 
Macquart,  which  is  said  also  to  occur  in  the  Philippines,  but  is  consid- 
ered a  doubtful  species  by  Griinberg. 


C.   The  Horn  Fly 

Family  Muscidce,  Genus  Hcematohia 

Introduction.  —  Hcematohia  serrata  R.  Desv.  ( =  Lyperosia  irritans  L.) 
is  commonly  called  the  horn  fly,  also  known  as  the  Texas  fly.  The 
former  name  is  applied  because  this  fly  has  the  habit  of  clustering, 
often  in  great  numbers,  at  the  base  of  the  horns  of  cattle.     Though 


BLOOD-SUCKING  MUSCIDS 


229 


in 


many  believe  the  fly  to  injure  the  horn,  there  is  no  foundation  for  this 
belief.  The  position  is  probably  only  sought  because  it  affords  a  safe 
resting  place,  especially  at  night. 

As  a  cattle  pest  the  horn  fly  has  few  if  any  equals ;  indeed,  in  the  San 
Joaquin  Valley  (California)  this  fly  is  regarded  as  the  most  serious 
pest.  The  horn  fly  is  a  comparatively  recent  introduction  into  the 
United  States  from  Europe,  where  it  has  been  an  important  cattle  pest 
for  many  years.  According  to  the  U.  S.  Bureau  of  Entomology  it  was 
first  reported  in  the  fall  of  1887  from  Camden,  N.  J.  appearing  during 
the  following  year  in  Maryland  and  Virginia,  probably  having  appeared 
in  Philadelphia  in  1886  and  by  1892  was  found  over  the  entire  continent 
from  Canada  to  Texas  and  from  Massachusetts  to  the  Rocky  Moun- 
tains. California  cattle  men  state  that  it  made  its  appearance  in  this 
state  in  about  1893-1894.     It  appeared  in  Honolulu,  Hawaii,  in  1897. 

Characteristics.  —  The  horn  fly  is  about  half  the  size  of  the  common 
house  fly,  i.e.  about  4  mm.  long.  It  has  much  the  same  color  and 
most  other  respects  resembles  the  Stomoxys  fly. 
The  mouth  parts  (Fig.  147)  are  as  in  Stomoxys 
except  that  the  labium  is  relatively  heavier  and 
the  palpi  are  almost  as  long  as  the  proboscis,  are 
flattened  and  loosely  ensheath  the  same.  The 
arista  is  plumose  dorsally.  The  wing  venation  is 
as  in  Stomoxys. 

These  flies  appear  early  in  spring  and  become 
most  abundant  in  late  summer  and  autumn. 
Both  cattle  and  horses  are  attacked,  but  most 
especially  the  former.  When  at  rest  on  the 
animal  or  elsewhere  the  wings  lie  flat  on  the  back 
and  fold  rather  closely,  but  when  the  fly  bites,  the 
wings  are  spread  and  the  insect  stands  perpen- 
dicularly, almost  hidden  between  the  hairs  of  the 
host.  Apparently  the  habit  of  resting  at  the  base  of  the  horns  is  only 
developed  when  flies  are  overabundant. 

Life  History.  —  The  horn  fly  deposits  its  eggs  chiefly,  if  not  exclu- 
sively, on  freshly  passed  cow  manure.  The  fly  is  seen  to  dart  from  the 
animal  and  deposit  its  eggs  in  groups  of  four  to  seven,  or  singly,  on  the 
surface  of  the  dung.  The  eggs  are  relatively  large  (1.3  to  1.5  mm.), 
larger  than  the  eggs  of  Stomoxys,  they  are  reddish  brown  in  color,  hence 
not  easily  seen  on  the  cow  dung.  Under  laboratory  conditions,  at  least, 
few  eggs  are  deposited  by  the  females,  —  rarely  over  twenty.  At  a 
temperature  of  24°  to  26°  C.  the  eggs  hatch  in  twenty-four  hours. 

The  larvse  burrow  beneath  the  surface  of  the  droppings,  reaching  full 
growth  in  from  three  to  five  days  when  they  crawl  underneath  into  drier 
parts  and  pupate.  The  pupal  period  requires  from  six  to  eight  days. 
Hence  the  entire  life  history  (Fig.  148)  from  the  egg  to  the  adult  requires 
from  ten  to  fourteen  days  at  a  temperature  of  from  24°  to  26°  C. 


Fig.  147.  —  Side  view  of 
head  of  the  hornfly, 
Hcematobia   serrata. 


230       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

Damage  Done.  —  The  damage  occasioned  by  the  horn  fly  is  chiefly 
through  irritation  and  annoyance  which  results  in  improper  digestion 
and  disturbed  feeding,  thus  producing  loss  of  flesh  and  reduction  of  milk 
in  dairy  animals.  Dr.  James  Fletcher  estimated  the  loss  in  Ontario 
and  Quebec  at  one  half  of  the  product  of  meat  and  milk.  Range  ani- 
mals literally  run  themselves  thin  in  trying  to  get  away  from  these  pests. 

The  actual  loss  of  blood  must  be  considerable  when  literally  thou- 
sands of  these  flies  attack  an  animal.  The  weakened  condition  thus 
produced  lays  the  animal  liable  to  disease.  From  ten  to  twenty-five 
minutes  are  required  for  the  fly  to  fully  engorge  itself;  during  this 
time  the  fly  withdraws  and  reinserts  its  proboscis  in  the  same  puncture 
many  times  as  in  a  pumping  motion.  Much  undigested  blood  is  dis- 
charged from  the  anus  of  the  fly  while  in  the  act  of  feeding. 


Fig.   148.  —  Life  history  of  the  "horn  fly,"  Hwmatobia  serrata.       X  4. 

Finally,  though  not  absolutely  proved,  except  through  inference,  the 
horn  fly  must  certainly  have  the  power  of  transmitting  infectious  blood 
diseases,  such  as  anthrax.  This  problem  has  as  yet  not  been  touched 
by  investigators. 

Control.  —  The  most  effective  method  to  prevent  the  multiplication 
of  the  horn  fly  is  to  scatter  the  droppings  from  cattle  with  a  rake  or 
other  implement  or  simply  by  dragging  a  dry  branch  over  the  field. 
Hogs  allowed  to  run  with  the  cattle  serve  this  purpose  very  w^ell.  The 
manure  thus  scattered  dries  out  quickly  and  the  larvse  if  present  perish 
owing  to  the  fact  that  they  require  much  moisture  for  development. 
The  writer  has  seen  this  method  applied  most  successfully  in  various 
parts  of  California  where  the  dry  summer  favors  this  mode  of  hand- 
ling the  fly.  On  wide  ranges  this  method  is  impracticable,  but  in 
connection  with  dairies  it  is  entirely  feasible.  Piles  of  cow  manure  re- 
moved from  stables  afford  a  good  breeding  place  for  the  Stomoxys  fly, 
especially  when  straw  predominates,  but  the  horn  fly  is  not  favored 
in  this  way  to  any  great  extent.  The  manure  should  either  be  stored 
temporarily  in  fly-tight  bins  like  horse  manure,  or  spread  on  the  field 


BLOOD-SUCKING  MUSCIDS  231 

at  once,  or  else  placed  in  containers  with  water  to  liquefy  the  manure, 
the  containers  to  be  covered. 

Animal  s'ljrays  used  as  repellents  are  of  various  kinds  and  of  various 
efficiencies.  Few  sprays  remain  effective  for  longer  than  a  day  or  so. 
Almost  any  oily,  greasy  substance  is  useful,  but  animals  thus  treated  in 
the  presence  of  dusty  roads  and  pasture  become  very  filthy  in  a  short 
time.  The  usual  ingredient  in  sprays  for  this  purpose  is  fish  oil  or 
train  oil,  though  petroleum  sprays  are  also  commonly  used.  The  latter 
are  not  to  be  recommended  for  use  on  very  hot  days. 

Petroleum  sprays  are  used  in  the  form  of  kerosene  emulsion  (crude 
petroleum,  2  gallons,  |  pound  soft  soap,  1  gallon  soft  water)  one  part  to 
five  parts  of  water.  The  Kansas  Experiment  Station  (Press  Bulletin 
No.  65)  recommends  the  following  mixture  as  both  cheap  and  efficient ; 
resin  (pulverized),  2  parts;  soap  shavings,  1  part;  water,  |  part;  fish 
oil,  1  part ;  oil  of  tar,  1  part ;  kerosene,  1  part ;  water,  3  parts.  The 
resin,  soap,  fish  oil  and  ^  part  water  are  boiled  together  until  the  resin 
is  dissolved,  then  add  the  three  parts  of  water  and  finally  the  kerosene 
and  oil  of  tar.  The  mixture  must  be  thoroughly  mixed  and  boiled  for 
fifteen  minutes.     The  cooled  mixture  is  then  ready  for  use  as  a  spray. 

The  application  of  the  spray  is  done  by  means  of  a  knapsack  spray 
pump  or  other  hand  sprayer.  One  application  seldom  remains  effective 
longer  than  three  days,  usually  only  a  few  hours.  The  addition  of  crude 
carbolic  acid  and  sulphur  is  strongly  recommended. 

Washburn  ^  states  that  "  very  fine  tobacco  dust  sifted  into  the  hair 
on  the  backs  and  w^here  it  will  find  lodgment,  and  the  above  wash  (a 
mixture  of  fish  oil  and  crude  carbolic  acid)  applied  to  other  parts  which 
will  not  hold  the  dust,  will  obtain  good  results." 

Smaller  herds  can  be  treated  with  ease  by  driving  the  animals  through 
a  narrow  passageway,  applying  the  spray  as  they  pass  between.  On  a 
larger  scale  it  has  been  shown  that  dipping  vat  methods  can  be  satis- 
factorily applied.  The  following  is  quoted  from  Circular  No.  115,  U.  S. 
Department  of  Agriculture,  Bureau  of  Entomology :  "  During  the  last 
three  years,  Mr.  J.  D.  Mitchell,  an  agent  of  the  Bureau,  working  with 
Mr.  W.  D.  Hunter  in  Texas,  has,  in  a  study  of  the  requirements  for 
horn  fly  control,  found  that  by  a  very  simple  modification  of  the  ordinary 
dipping  vat  a  very  large  percentage  of  the  flies  on  cattle  can  be  destroyed, 
with  the  consequent  very  notable  limiting  of  the  loss  from  the  fly  pest. 
With  the  vats  as  ordinarily  constructed,  most  of  the  flies  abandon  the 
animal  at  the  moment  it  plunges  into  the  vat  and  escape,  and  go  to  other 
animals,  and  ultimately  with  the  drying  of  the  dipped  animal  return  to 
it.  Mr.  Mitchell  found,  however,  that  by  putting  a  splash  board  near 
the  top  of  the  vat  on  either  side,  about  four  feet  above  the  level  of  the 
dip,  the  water  thrown  up  violently  as  the  animal  plunges  in,  is  caught  by 

1  Washburn,  F.  L.,  1905.  Diptera  of  Minnesota:  two-winged  flies  affect- 
ing the  farm,  garden,  stock  and  household.  Univ.  of  Minnesota  Agr.  Exp. 
Sta.,  Bull.  No.  93. 


232       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

these  splash-boards  and  is  thrown  back  as  a  spray,  filling  the  air  space 
above  the  animal  and  drenching  and  destroying  the  flies  in  their  effort 
to  escape.  The  few  of  the  horn  flies  that  may  escape,  together  with 
those  which  abandoned  the  animal  at  the  entrance  to  the  vat,  were 
observed  to  hover  or  settle  on  the  chute  fence,  and  many  would  alight 
on  the  next  animal  coming  along.  He  also  found  that  where  the  ani- 
mals have  been  heated  in  corralling  and  getting  them  into  the  chute  the 
flies  stick  much  closer  and  are  much  less  apt  to  take  quick  flight,  thus 
insuring  the  capture  of  a  larger  percentage  of  them  by  the  dip  and 
spray."     An  oily  dip  must,  of  course,  be  used  for  this  purpose. 


CHAPTER   XVI 

MYIASIS 

Flesh  Flies,  Botflies,  Warble  Flies,  etc. 

Myiasis  is  a  term  referring  to  the  presence  of  and  resultant  disturb- 
ances traceable  to  insect  larvae,  primarily  Diptera,  in  the  intestme 
(intestinal  myiasis),  stomach  (gastric  myiasis),  subcutaneous  tissue 
(dermal  or  cutaneous  myiasis),  muscles  (muscular  myiasis),  frontal  si- 
nuses (nasal  myiasis),  or  ears  (auricular  myiasis)  of  vertebrate  animals. 
The  responsible  insects  may  relate  to  myiasis  in  a  more  or  less  accidental 
manner,  as  is  the  case  with  certain  root  maggot  flies,  or  they  may  be  ob- 
ligatory parasites,  as  is  true  of  the  bot  and  warble  flies. 

Dipterous  Larvse.  —  The  larvse  of  Dipterous  insects  are  footless  and 
are  commonly  called  maggots.  Owing  to  the  environmental  setting  of 
the  parasitic  species  they  may  be  mistaken  for  "  worms  "  and  are  com- 
monly so  designated.  Owing  to  differences  in  prophylactic  measures 
insect  larvae  and  helminths  should  be  carefully  distinguished,  ihe 
dipterous  larva  are  as  a  rule  short  and  plump,  measuring  from  5  to  35 
mm.  in  length  (less  in  very  young  larvse),  and  from  1  to  12  mm.  in 
diameter ;  they  are  more  or  less  cylindrical  and  tapering  in  form ;  are 
distinctly  segmented,  with  ordinarily  11  or  12  visible  segments  (l^ig. 
13).  All  insect  larvae  (as  well  as  adults)  possess  an  internal  system  ot 
tracheated  tubules,  the  respiratory  system,  which  worms  do  not  possess, 
hence  with  even  a  very  minute  portion  of  the  parasite  at  hand,  one  can 
readily  determine  whether  the  specimen  is  insectan  or  not. 

All  nematode  worms  with  which  maggots  might  most  easily  be 
confused  are  non-segmented.  Annelids  with  which  insect  larvae  might 
also  be  confused  owing  to  their  cylindrical,  often  plump  form  and 
their  common  segmentation,  are  easily  distinguished  from  the  fact  that 
the  former  possess  a  larger  number  of  segments  (certainly  over  20) 
and  are  devoid  of  tracheal  tubules.  Other  important  zoological  char- 
acters are,  of  course,  recognized. 

A.    The  Flesh  Flies 

Order  Diptera,  Family  Sarcophagid(E 

Adult  Characteristics.  —  The  larvae  or  maggots  of  the  flesh  flies  are 
met  with  most  frequently  in  myiasis  of  all  forms.  The  adult  flies  are 
commonly  known  as  blowflies.     The  great  majority  of  the  species  de- 

233 


234 


MEDICAL  AND  VETERINARY  ENTOMOLOGY 


posit  their  rather  conspicuous  ghstening  white  eggs  on  meat,  dead  ani- 
mals, excrement  or  decaying  vegetable  matter ;  several  species,  notably 
the  gray  flesh  flies  (Sarcophaga)  deposit  living  young.  The  blowflies 
are  commonly  included  with  the  Muscidse,  but  by  following  Girschner's 
classification  based  on  thoracic  bristles  all  of  the  typical  flesh-feeding 
flies  are  conveniently  classed  among  the  Sarcophagidse.  The  Sarcoph- 
agids  are  as  a  rule  large  flies,  the  smallest  being  about  the  size  of  the 
house  fly ;  the  wing  venation  is  of  the  Muscid  type ;  in  color  they  vary 
from  a  bright  metallic  green  and  blue  to  gray ;  the  thorax  is  more  or 
less  densely  covered  with  bristles  or  heavy  hairs  (the  Tachinid  flies 
with  which  the  Sarcophagids  are  most  easily  confused  have  tufts  of  very 
long  spines  on  the  tip  of  the  abdomen,  and  the  arista  is  bare). 

Chrysomyia  (Compsomyia)  macellaria  Fabr.  is  the  most  important 
member  of  the  family.^  This  fly  is  commonly  known  as  the  Texas 
screw  worm  fly,  probably  because  the  larva  is  pro- 
vided with  intersegmentally  arranged  short  spines 
and  papillae  which  give  it  a  more  or  less  screw- 
like appearance.  The  fly  (Fig.  149)  varies  in  size 
from  10  to  13  mm.,  dependent  upon  the  growth 
of  the  larva  ;  the  ground  color  is  a  metallic  green, 
with  three  longitudinal  dark  stripes  on  the  tho- 
rax ;  the  head  is  reddish  to  yellowish  brown  ;  the 
wings,  when  at  rest  are  commonly  folded  scissors- 
like  over  the  abdomen ;  the  wing  venation  is 
similar  to  that  of  the  house  fly  {Musca  domestica) . 
The  screw  worm  fly  is  typically  a  North  and 
South  American  fly  ranging  from  Patagonia  to 
Canada. 

Life  History.  —  The  screw  worm  fly  over- 
winters most  commonly  in  the  pupal  stage,  but, 
no  doubt,  also  hibernates  as  an  adult  as  do  the  bluebottle  and  green- 
bottle  flies.  Chrysomyia  macellaria  deposits  eggs  normally  within  its 
southern  range,  the  time  for  hatching  varying  from  less  than  an  hour 
to  twelve  or  more  hours.  But  there  is  some  difference  of  opinion  as 
to  its  habits  in  its  northern  range.  The  writer  has  carried  on  careful 
observations  on  this  fly  during  several  summers  along  the  southern 
border  of  Lake  Erie  and  has  never  observed  this  fly  to  lay  eggs.  Liv- 
ing young  were  invariably  deposited.  Others  (notably  Hine)  maintain 
that  eggs  are  deposited.  It  is  quite  possible  that  the  latter  is  true 
earlier  in  the  summer. 

The  eggs  or  larvse  to  the  number  of  200  to  500  are  deposited  on  dead 
animals  ordinarily,  or  in  wounds  or  sores  of  domesticated  or  wild  ani- 

'  For  a  detailed  account  of  the  ecological  relationships  of  the  Sarcophagidae 
the  reader  is  referred  to  the  writer's  work  "An  ecological  and  experimental 
study  of  Sarcophagidse,  etc."  Journ.  of  Exp.  Zool.,  Vol.  4,  No.  1,  pp.  45-83. 
Also  "The  sensory  reactions  of  Sarcophagid  flies,  etc."  Journ.  of  Exp.  Zool., 
Vol.  10,  No.  2,  pp.  167-226. 


Fig.  149.  —  Chrysomyia 
macellaria,  the  Texas 
screw  worm  fly.     X  3.5. 


MYIASIS 


235 


mals.  Human  beings  are  frequently  attacked  in  the  nostrils.  The 
growth  of  the  larvae  is  very  rapid,  full  size  being  reached  in  three  days 
under  optimum  conditions.  The  fully  grown  maggots  vary  from  12  to 
15  mm.  in  length ;  food  shortage  (except  when  very  great)  as  a  rule  only 
results  in  smaller  larvfe  and  smaller  flies. 

When  fully  grown  the  larvse  leave  the  carcass  or  wound,  bury  them- 
selves in  loose  earth  or  debris  immediately  beneath  or  near  by,  and 
enter  the  pupal  stage  in  two  or  three  days.  The  pupje  are  chestnut- 
colored,  barrel-shaped,  rather  rough  and  fairly  characteristic,  measuring 
from  5  to  8  mm.  in 
length.  Under  op- 
timum conditions 
the  pupal  stage  re- 
quires four  days. 

On  emergence 
from  the  pupal  cases 
the  flies  crawl  out 
of  the  sand  or  dirt 
and  climb  up  near- 
by grasses,  weeds  or 
shrubbery,  where 
the  wings  are  spread . 
The  screw  worm  fly 
at  this  time  almost 
invariably  turns 
about  with  its  head 
downward  after  it 
has  reached  a  rest- 
ing place.  (Fig.  150.) 
Thus  one  often  finds 
great  numbers  of 
flies  in  some  re- 
stricted spot  with- 
out an  apparent  ex- 
planation for  their 
presence.  The  total  life  history  of  the  screw  worm  fly  from  egg  (or 
maggot)  to  imago  is  nine  days  at  its  shortest  to  two  weeks  and  over 
under  less  favorable  conditions. 

As  Affecting  Man  the  attacks  of  this  fly  are  largely  limited  to  in- 
dividuals suffering  from  nasal  catarrh  or  unclean  from  vomit  or  with 
open  sores  or  wounds.  Sleeping  individuals  or  persons  in  a  drunken 
stupor  are  most  liable  to  be  attacked,  although  the  fly  has  been  known 
to  dash  successfully  into  the  nostrils  of  wide-awake  individuals,  in 
which  case  the  fly  is  usually  not  permitted  to  remain  in  the  nostrils 
long  enough  to  oviposit.  Even  so  it  is  wise  to  properly  syringe  the 
nasal  passages. 


Fig.  150.  —  Texas  screw  worm  flies  just  emerged  from  the 
pupa  cases.  A  dead  animal  near  by  furnished  food  for  the 
larvae,  pupation  took  place  in  the  sand  underneath  the 
carcass.  The  newly  emerged  flies  have  crawled  up  on  the 
grass  and  will  soon  be  ready  to  fly  away.  Note  character- 
istic resting  attitude,  with  head  down. 


236       MEDICAL  AND   VETERINARY   ENTOMOLOGY 

The  following  quotation  will  sufficiently  explain  the  nature  of  the 
injury  produced.  (See  Osborn,  1896,  pp.  127-128,  quoting  Richardson 
in  Peoria,  III.  Med.  Mo.  for  February,  1883.) 

"While  traveling  in  Kansas  in  the  latter  part  of  last  August,  a  citizen  of 
this  place  had  the  misfortune  to  receive  while  asleep  a  deposit  of  eggs  from  this 
fly.  He  had  been  troubled  for  years  with  catarrh,  hence  the  attraction  to  the 
fly.  He  returned  home  a  few  days  after  the  accident  and  shortly  after  began 
complaining  of  a  bad  cold.  Growing  rapidly  worse,  I  was  caUed  to  attend  him. 
Monday,  my  first  day,  his  appearance  was  that  of  a  man  laboring  under  a 
severe  cold.  Had  slight  congestion  of  the  lungs,  and  moderate  fever.  His 
nose  seemed  greatly  swollen  and  he  complained  of  a  smarting,  uneasy  feeling 
in  it,  and  general  misery  through  the  head.  Gave  him  treatment  to  relieve  the 
congestion  and  fever.  Tuesday,  saw  him  again.  His  nose  and  face  were  still 
swollen,  and  in  addition  to  the  other  symptoms  he  was  becoming  slightly  de- 
lirious and  complained  a  great  deal  of  the  mtense  misery  and  annoyance  in  his 
nose  and  head.  A  few  hours  after,  I  was  sent  for  in  haste  with  the  word  that 
something  was  in  his  nose.  I  found  on  examination  a  mass  of  the  larva?  of  this 
fly  (or  '  screw  worms '  as  they  are  commonly  caUed  in  the  South)  completely 
blocking  up  one  nostril.  On  touching  them  they  would  instantly  retreat  en 
masse  up  the  nostril.  Making  a  20  per  cent  solution  of  chloroform  in  sweet  mUk 
I  made  a  few  injections  up  both  nostrils,  which  immediately  brought  away  a 
large  number,  so  that  in  a  few  hours  I  had  taken  away  some  125  of  them.  By 
Wednesday  evening  erysipelas  had  begun,  implicating  the  nose  and  neighboring 
portions  of  the  face.  Another  physician  was  called.  By  continual  syringing 
with  a  strong  antiseptic  solution  of  salicylate  of  soda,  bicarbonate  of  soda,  and 
carbolic  acid  we  hoped  to  drown  out  the  remaining  larvae.  But  they  had  by 
this  time  cut  their  way  into  so  many  recesses  of  the  nose  and  were  so  firmly  at- 
tached that  we  were  unable  to  accomplish  much.  Finally  we  resorted  to  the 
chloroform  injections,  which  immediately  brought  away  a  considerable  number. 
Friday  I  was  able  to  open  up  two  or  three  canals  that  they  had  cut,  extracting 
several  more  that  had  literally  packed  themselves,  one  after  another,  in  these 
fistulous  channels.  His  speech  becoming  suddenly  much  worse,  I  examined  the 
interior  of  his  mouth  and  found  that  a  clear-cut  opening  had  been  made  entirely 
through  the  soft  palate  into  his  mouth  and  large  enough  to  insert  the  end  of  a 
common  lead  pencil.  Saturday  the  few  remaining  larva^  began  changing  color 
and  one  by  one  dropped  away.  On  Sunday  for  the  first  tune  hemorrhage  from 
both  nostrUs  took  place,  which  continued  at  intervals  for  three  days,  but  was 
not  at  any  time  severe.  On  this  day  the  patient  began  to  unprove,  the  delirium 
and  erysipelas  having  subsided,  leaving  but  little  or  no  annoyance  in  his  head. 
In  a  few  daj^s  he  became  able  to  go  about  home,  and  even  to  walk  a  distance 
of  half  a  mile  to  visit  a  friend  and  return.  But  while  there  he  began  complain- 
ing of  a  pain  in  the  neighborhood  of  his  left  ear,  apparently  where  the  eustachian 
tube  connects  with  the  middle  ear.  It  proved  to  be  an  abscess.  Being  already 
so  reduced  by  the  first  attack  he  was  unable  to  withstand  the  second,  and  died 
after  an  Ulness  of  nearly  three  weeks,  completely  exhausted  by  his  prolonged 
sufferings.  Three  days  before  his  death  the  abscess  discharged  its  contents  by 
the  left  nostril.     The  quantity  of  pus  formed  was  about  2^  ounces  (78  grams). 

"In  all  about  250  larvae  were  taken  away  from  him  during  the  first  attack, 
and,  as  the  visible  results,  not  only  had  they  cut  the  hole  through  the  soft  palate, 
but  had  also  eaten  the  cartilage  of  the  septum  of  the  nose  so  nearly  through  as 
to  give  him  the  appearance  of  having  a  broken  nose.  The  case  occupied,  from 
the  first  invasion  of  the  fly  to  its  final  result,  nearly  two  months.  He  doubtless 
would  have  recovered  but  for  the  fonnation  of  the  abscess,  which,  from  all  the 
symptoms,  was  caused  by  one  or  more  of  the  larvae  having  found  their  way  up 
the  left  eustachian  tube." 


MYIASIS  237 

As  Affecting  Domesticated  Animals.  —  According  to  Osborn  ^  cattle 
suffer  most  from  the  ravages  of  screw  worms,  in  which  they  occur  in 
wounds  from  horns,  castrating,  spraying,  branding,  dehorning,  barbed 
wire  injuries,  and  often  where  ticks  have  burst  on  the  brisket,  flank  or 
just  behind  the  udder  of  cows.  They  often  occur  in  the  vulvae  of  fresh 
cows,  especially  if  there  has  been  a  retention  of  the  placenta  or  after- 
birth. Young  calves  are  almost  invariably  affected  in  the  navel,  and 
often  in  the  mouth,  causing  the  teeth  to  fall  out. 

Horses  and  mules  are  not  so  often  attacked,  and  if  so,  the  maggots 
are  usually  found  in  barbed  wire  injuries,  and  occasionally  in  the  sheaths 
of  horses  and  the  vaginae  of  mares  and  the  navels  of  colts. 

Hogs  on  the  other  hand  are  more  liable  to  become  affected  than  horses, 
since  they  are  frequently  wounded  by  dogs  and  by  fighting  or  there  may 
be  barbed  wire  injuries,  wounds  from  castration,  etc. 

"  Sheep  are  attacked  when  injured  by  dogs ;  or  when  the  sheep  are 
in  poor  condition  the  eggs  are  laid  upon  the  wool,  and  when  the  larvae 
hatch  they  immediately  bore  into  the  skin.  In  many  cases  the  sheep 
are  attacked  within  the  nasal  cavities  and  the  worms  eat  into  the  head." 
The  reader  is  warned  against  confusing  these  maggots  with  the  true 
head  maggot  {CEstrus  ovis). 

Other  Flesh  Flies.  —  The  larvae  of  several  species  of  flesh  flies  are 
frequently  met  with  in  gastric  and  intestinal  myiasis.  This  is  accounted 
for  by  the  presence  of  very  young  maggots  in  meats  which  are  eaten  cold 
and  not  carefully  masticated.  Nausea  and  gastric  disturbances  may  be 
traceable  to  this  form  of  accidental  myiasis.  Owing  to  the  small 
amount  of  oxygen  available  the  growth  of  the  larvae  must  needs  be  very 
slow.  Larvae  brought  to  the  attention  of  the  writer  have  been  seldom 
more  than  4  or  5  mm.  long. 

The  flesh  flies  deposit  their  eggs  commonly  on  cold  meat,  particularly 
pork,  if  exposed  to  flies.  The  eggs  hatch  in  from  eight  to  twenty- 
four  hours  under  summer  conditions  and  the  larvae  grow  rapidly. 

The  larvae  of  these  several  species  also  occur  frequently  in  wounds 
in  domesticated  animals  and  man,  producing  injury  similar  to  that  of 
the  screw  worm. 

The  larvae  of  the  blowfly  or  bluebottle,  Calliphora  vomitoria  Linn, 
and  C.  erythrocephala,  Mg.  (Fig.  117e)  are  most  commonly  met  with. 
The  two  species  of  flies  are  not  usually  differentiated,  the  two  names 
being  applied  indiscriminately.  C.  vomitoria,  however,  has  black  genae 
with  golden  red  hairs,  while  C.  erythrocephala  has  fulvous  genae  with 
black  hairs.  The  eggs  of  these  species  hatch  in  from  six  to  forty-eight 
hours,  the  growing  larvae  feed  on  the  flesh  for  from  three  to  nine  days, 
after  which  the  fully  grown  larvae  leave  the  food  and  bury  themselves 
in  loose  earth.  This  period  (prepupal  period)  lasts  from  two  to  seven 
days,  commonly  four,  after  which  pupation  takes  place.  The  pupal 
period  varies  considerably  according  to  temperature,  lasting  from  ten 

1  Oslsorn,  Herbert,  1896  {loc.  ciL). 


238       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


to  seventeen  days,  commonly  eleven  days.  Thus  the  life  history  of  the 
blow  fly  requires  from  sixteen  to  thirty-five  days,  commonly  twenty-two 
days.     The  life  of  the  adult  is  about  thirty-five  days  on  an  average.^ 

Lucilia  ccBsar  Linn.  (Fig.  117f/),  the  greenbottle  fly,  is  not  so  commonly 
found  indoors  and  is  typically  a  scavenger  fly.  The  life  history  of  this 
species  is  somewhat  shorter  than  that  of  the  bluebottle.  The  egg  stage 
requires  from  six  to  forty-eight  hours  ;  the  growing  (feeding)  larval  stage 
requires  from  three  to  seven  days,  commonly  five  days ;  the  prepupal 
period,  commonly  six  days ;  and  the  pupal  period  from  eight  to  thirty- 
four  days,  commonly  twelve  days,  giving  a  total  of  from  sixteen  to 
sixty  days  and  over,  commonly  twenty-four  days.  Under  optimum 
conditions  this  fly  invariably  requires  Mteen  days  for  its  metamorphosis; 
the  average  longevity  of  the  fly  is  about  thirty  days. 

Lucilia  sericata,  Mg.  is  popularly  known  as  the  "sheep  maggot  fly" 
owing  to  its  frequent  occurrence  on  sheep.  This  fly  resembles  Lucilia 
ccBsar  very  closely,  and  its  larvae  resemble  the  larvae  of  the  latter  even 
more  closely.  The  female  deposits  her  eggs  commonly  in  the  soiled 
wool  of  lambs  and  sheep.  Animals  suffering  from  diarrhea  are  particu- 
larly subject  to  attack.  The  newly  hatched  larvae  live  either  in  the 
matted  wool  next  the  skin  or  burrow  under  the  skin  particularly  at 
points  that  have  been  injured  by  ticks  or  in  other  ways. 

The  damage  done  by  the  larvae  is  often  quite  great.     The  metamor- 
phosis and  time  requirement  for  the  larval  and  pupal  periods  are  quite 
similar  to  Lucilia  ccesar  and  the  damage  done  is  similar 
to  that  of  Chrysomyia  macellaria.    Phormia  regina  Meig. 
is  also  an  important  sheep  maggot  fly  in  California. 

Sarcophaga  sarracenioe  Riley  is  a  typical  flesh  fly,  has 
the  appearance  of  an  overgrown  house  fly,  but  is  lighter 
gray,  has  a  spiny  thorax,  brighter  reddish  brown  eyes 
and  is  viviparous.  It  resembles  very  closely  the 
larger  species  of  parasitic  Tachinid  flies,  but  has  not 
the  strongly  developed  terminal  abdominal  spines.  The 
young  are  deposited  on  meat,  or  if  extruded  in  the  vicin- 
ity of  meat  not  accessible  to  the  fly,  the  larvae  crawl  to 
the  food.  The  larval  stage  under  optimum  conditions 
requires  about  five  days,  and  the  pupal  period  about 
thirteen  days. 

Several  African  species  of  flesh  flies  are  commonly 
referred  to  in  the  literature  on  myiasis,  among  them 
Cordylobia  anthropophaga,  E.  Blanch.,  the  "  tumbu  fly,' 
the  larvae  of  which  burrow  beneath  the  skin,  developing  there  as  do  the 
larvae  of  the  warble  fly,  Hypoderina.  It  is  said  that  babies  are  par- 
ticularly liable  to  be  attacked  by  the  "tumbu  fly."  Austen  describes 
it  as  being  a  "  thickset,  compactly  built  fly,  of  an  average  length  of 


Fig.   151.  — The 
Congo        floor 
maggot,  Audi 
meromyia  lute- 
ola.      X  2.5. 


1  Herms,  W.  B.,   1911.      The    photic   reactions    of    Sarcophagid    flies,    etc. 
Contributions  from  the  Zool.  Lab.  of  the  Mus.  of  Comp.  Zool.,  Harvard,  No.  217. 


MYIASIS  239 

mm.  .  .  .  Head,  body  and  legs  straw  color.  ..."  Another 
species  commonly  found  in  the  same  locality  with  the  above  is 
Auchmeromyia  luteola,  Fabr.  The  larva  is  a  blood-sucker  and  is  known 
as  the  "  Congo  floor  maggot."  (Fig.  151.)  The  two  species  are  said 
to  resemble  each  other  closely  but  Graham-Smith  ^  states  that  "  the  two 
species  may  be  distinguished  by  the  fact  that  in  A.  luteola  the  eyes  are 
wide  apart  in  both  sexes,  the  body  is  narrower  and  more  elongate,  the 
hypopygidium  of  the  male  is  in  the  form  of  a  conspicuous,  forwardly 
directed  hook,  for  which  the  ventral  half  of  the  penultimate  segment  of 
the  abdomen  serves  as  a  sheath ;  and  lastly,  by  the  fact  that  the  second 
abdominal  segment  in  the  female  is  twice  the  length  of  the  same  segment 
in  the  male.  ..." 


"The  full-grown  larva  is  a  fat,  yellowish  white  maggot,  12  to  121  mm.  in 
length,  bluntly  pointed  at  the  anterior  or  cephalic  extremity,  and  truncate  be- 
hind ;  its  greatest  breadth  (on  the  sixth  and  seventh  segments)  is  5  mm.  The 
body  consists  of  twelve  visible  segments,  the  divisions  between  which  are  strongly 
marked,  except  between  the  cephalic  and  first  body  segment  (the  latter  of  which 
bears  the  anterior  or  prothoracic  stigmata,  or  respiratory  apertures),  and  be- 
tween the  eleventh  and  twelfth  segments.  On  the  underside  of  the  cephalic 
segment  the  tips  of  the  black  paired  mouth  hooks  may  be  seen  protruding,  while 
in  a  slight  depression  in  the  flattened  posterior  surface  of  the  twelfth  segment 
are  situated  the  paired  posterior  stigmatic  plates.  In  the  adult  larva  the  slit- 
like apertures  in  these  plates  are  not  very  easy  to  distinguish,  but  in  a  maggot 
in  the  second  or  penultimate  stage,  it  is  seen  that  each  plate  bears  three  ridges 
of  tawny  colored  chitin ;  these  ridges  run  obliquelj^  downwards  and  outwards, 
at  an  angle  of  45°  from  the  median  line,  and,  while  the  median  ridge  on  each 
plate  is  nearly  straight,  the  other  two  ridges  are  characteristically  curved,  re- 
sembling inverted  notes  of  interrogation,  with  the  concavity  directed  towards 
the  median  ridge.  The  segments  of  the  body  are  transversely  wrinkled  on  the 
dorsal  and  ventral  surfaces  (especially  on  the  latter),  and  puckered  on  the  sides. 
From  the  third  to  the  eleventh  segment  the  body  is  thickly  covered  with  minute 
recurved  spines  of  brownish  chitin  (darker  in  the  case  of  larva?  ready  to  leave  the 
host),  usually  arranged  in  transverse  series  or  groups  of  two  or  more,  which 
can  be  seen  to  form  more  or  less  distinct,  undulating  or  irregular,  transverse 
'  rows.     These  spines  will  be  described  in  somewhat  greater  detail  below. 

"Above  and  to  the  outer  side  of  each  mouth  hook  is  an  antenna-like  pro- 
tuberance, which,  as  in  the  case  of  the  larva  of  the  blowfly  {Calliphora  erythro- 
cephala  Mg.),  exhibits  a  pair  of  light  brown,  ocellus-like  spots,  or  rather  papilla?, 
placed  one  above  the  other.  In  a  small  larva,  5  mm.  in  length,  from  Lagos,  the 
papilla?  are  very  clearly  visible ;  each  papilla  is  surrounded  by  a  ring  of  pale 
brownish  chitin,  and  its  shape,  when  viewed  from  the  side,  is  exactly  that  of  a 
muzzle  of  an  old-fashioned  muzzle-loading  cannon. 

"This  small  larva  also  shows  on  the  basal  segment  of  each  antenna,  or  an- 
tenna-like protuberance,  below  and  a  little  to  the  outer  side  of  the  mouth  hook, 
a  prominence  bearing  a  series  of  about  six  small,  brown  tipped,  chitinous  spines. 
In  the  same  larva  the  spines  on  the  body  are  most  conspicuous,  and  most  strongly 
developed  and  chitinized,  on  the  fifth,  sixth  and  seventh  segments.  The  tenth 
and  eleventh  segments  are  also  covered  with  spines,  but,  since  the  chitin  of 
which  they  are  composed  is  not  tinged  with  brown,  these  segments  appear  bare. 

1  Graham-Smith,  G.  S.,  1913.  Flies  in  relation  to  disease,  —  non-blood- 
sucking flies.     Cambridge  University  Press,  xiv  +  292  pp. 


240       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

In  the  adult  larva  also,  the  spines  of  the  tenth  and  eleventh  are  less  conspicuous 
than  those  on  the  preceding  segments;  on  the  twelfth  segment,  which  bears 
the  posterior  stigmatic  plates,  the  spines  are  very  minute.  Fully  chitinized 
spines  are  dark  brown,  but  this  color  is  generally  confined  to  the  apical  half 
of  the  spine,  or  may  be  absent  from  the  extreme  base.  In  shape  each  spine 
is  a  short  cone,  with  the  apex  recurved,  pointing  towards  the  hinder  part  of  the 
body.  The  spines  are  broad  at  the  base  in  proportion  to  their  length,  and  not 
infrequently,  especially  on  the  under  side  of  the  body,  are  bifid  at  the  tip.  They 
are  closest  together  and  most  strongly  developed  on  the  anterior  portion  of 
each  segment,  becoming  smaller  and  showing  a  tendency  to  disappear  towards 
the  hind  margin.  They  are  arranged  in  irregular  transverse  rows,  which  are 
usually  seen  to  be  composed  of  from  two  to  five  spines,  placed  side  by  side. 

"In  the  adult  larva  the  median  area  of  the  ventral  surface  of  the  segn^ents 
five  (or  six)  to  eleven  inclusive  is  marked  with  a  series  of  three  transverse  ridges, 
which  are  most  prominently  developed  on  the  seventh  and  following  segments. 
On  each  segment  the  foremost  ridge  is  the  shortest ;  next  in  length  comes  the 
hindmost,  and  the  middle  ridge  is  the  longest  of  the  three,  curling  round  the 
posterior  ridge  at  each  end.  Similar  but  less  strongly  marked  ridges  are  seen 
on  the  dorsal  surface. 

"  Puparium.  Of  the  usual  barrel-shaped  Muscid  type.  Average  dimensions : 
length  IO5,  greatest  breadth,  4f  mm.  Though  at  first  of  a  ferruginous  or 
light  chestnut  tint,  the  puparium  gradually  darkens  until  it  becomes  'seal- 
brown'  or  practically  black." 

Manson  {loc.  cit.)  states  that  the  fly  deposits  its  eggs  in  the  dust- 
filled  cracks  and  crevices  of  the  mud  floors  of  native  huts,  particularly 
in  spots  where  urine  is  voided.  The  duration  of  the  larval  life  has  not 
been  determined.  The  larvse  suck  blood  mainly  at  night.  The  pupal 
stage  is  said  to  require  from  two  to  three  weeks. 

Treatment  for  Nasal  Myiasis  in  Humans.  —  Treatment  for  maggots 
in  the  frontal  sinuses  and  other  cavities  must  be  given  without  delay, 
owing  to  the  rapid  growth  of  the  maggots  and  their  terrible  destructive 
work.  Injection  of  a  myiacide  is  necessary.  Some  of  the  more  useful 
remedies  are  "  20  per  cent  solution  of  chloroform  in  sweet  milk,  a  few 
injections  up  both  nostrils,"  repeat  until  larvae  are  expelled ;  or  carbolic 
acid  2  per  cent ;  or  infusion  of  pyrethrum  ;  or  turpentine.  A  saturated 
solution  of  common  salt  will  cause  only  a  portion  of  the  larvae  to  be  ex- 
pelled but  is  not  to  be  disregarded  in  the  absence  of  more  useful  remedies, 
until  a  physician  arrives. 

Treatment  for  Animals.  —  After  locating  the  point  of  infestation, 
indicated  by  purulent  sores,  or  small  eaten  openings,  surrounded  by  ele- 
vations which  shift  or  disperse  suddenly  when  touched,  the  expulsion 
of  the  maggots  must  be  brought  about  by  the  introduction  of  an  insecti- 
cide. Ordinarily  a  weak  solution  of  carbolic  acid  (1|  to  2  per  cent), 
pyrethrum  infusion,  chloroform,  creolin  or  chloronaphtholeum  is  injected. 
This  may  be  done  as  recommended  by  Francis  by  means  of  a  machinist's 
oiling  can.  The  larvae  must  then  be  carefully  scraped  out  and  the  wound 
dressed  with  pine  tar  or  other  curative  agent.  Pine  tar  will  also  act  as 
a  repellent  against  further  attack  by  flies. 

Preventive  Measures.  —  To  prevent  immediate    attack    by  flies. 


MYIASIS  241 

animals  should  be  carefully  examined  for  open  wounds,  wire  fence 
cuts,  etc.,  so  as  to  apply  treatment  and  repellents  to  prevent  the  deposi- 
tion of  eggs. 

Inasmuch  as  the  flies  involved  in  myiasis  breed  very  abundantly 
in  dead  animals,  all  carcasses  should  be  burned  without  delay  or  buried 
deeply  and  the  body  liberally  covered  with  "  chloride  of  lime."  Burning 
is  preferable  by  far.  Superficially  buried  carcasses  are  easily  reached  by 
the  young  maggots  hatching  from  eggs  deposited  on  the  ground  above 
the  body.  Proper  and  expeditious  disposal  of  all  dead  bodies,  such  as 
rats,  cats,  dogs,  or  larger  animals,  also  of  slaughter  house  refuse,  kitchen 
garbage,  manures,  etc.,  will  certainly  reduce  the  myriads  of  flies  which 
are  a  menace  to  the  health  and  well-being  of  both  man  and  beast  on  the 
farm. 

B.   Anthomyid  Flies 

Order  Diptera,  Family  AnthomyidcB 

Characteristics.  —  The  Anthomyid  flies  (Fig.  117c)  are  usually 
grayish  in  color,  non-metallic  resembling  the  house  fly.  The  first 
posterior  cell  of  the  wings  is  broadly  open.  The  mouth  parts  are  of 
the  house  fly  type.  The  larvse  are  often  vegetable  feeders,  either  in 
living  roots  or  in  decaying  vegetation,  also  in  manures.  The  meta- 
morphosis is  complex  as  in  the  house  fly. 

Because  the  maggots  of  the  Anthomyid  flies  are  commonly  found  in 
onions,  radishes,  turnips  and  other  roots  and  vegetation,  their  relation 
to  human  myiasis  is  easily  understood,  particularly  when  the  vegetable 
is  eaten  uncooked.  Several  species  of  Anthomyid  larvae  have  been 
recovered  in  human  cases,  notably  Fannia  (Homalomyia)  canicularis, 
F.  scalaris,  Anthomyia  radicum. 

Fannia  {Homalomyia)  canicular  is  L.,  commonly  known  as  the  lesser 
house  fly,  is  frequently  seen  hovering  in  mid-air  or  flying  hither  and 
thither  in  the  middle  of  the  room.  Where  the  common  house  fly  is  en- 
countered most  abundantly  in  the  kitchen  or  dining  room,  particularly 
on  food,  the  "little  house  fly"  will  be  seen  as  commonly  in  one  room  as 
another,  and  very  seldom  actually  on  the  "spread"  table.  The  writer 
commonly  observes  a  half  dozen  or  more  of  these  little  flies  dancing 
weirdly  in  the  center  of  the  lecture  room  midway  between  the  floor 
and  the  ceiling.  Various  observers  have  estimated  that  this  species 
constitutes  from  one  to  25  per  cent  of  the  total  population  of  flies  in  the 
house. 

In  size  the  species  varies  from  5  to  6  mm.  Its  color  is  grayish,  re- 
sembling the  house  fly  very  closely.  Hewitt  describes  the  male,  viz., 
"  Head  iridescent  black,  silvery  white,  especially  around  the  eyes.  The 
antennae  are  blackish  gray  with  non-setose  arista.  Palps  black.  The 
thorax  is  blackish  gray  with  three  indistinct  black  longitudinal  stripes ; 
the  scutellum  is  gray  and  bears  long  setae ;   the  sides  of  the  thorax  are 


242       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


lighter.  .  .  .  The  legs  are  black  and  the  middle  femora  bear  comb- 
like setse  below.  The  somewhat  large  squamse  at  the  bases  of  the  wings 
are  white  and  the  halteres  are  yellow.  .  .  .  The  head  of  the  female  is 
gray  with  a  wide  frons,  black  frontal  stripe  and  gray  sides.  The  longi- 
tudinal stripes  of  the  thorax  are  faint  and  the  abdomen,  which  is  more 
pyriform  than  that  of  the  male,  has  a  slightly  golden  attachment." 

The  eggs  of  this  species  are  deposited  on  decaying  vegetable  matter 
and  excrement,  particularly  of  humans,  horses  and  cows.  The  larvae 
emerge  in  about  24  hours  and  may  be  recognized  as  compressed,  spiny 
organisms  about  6  mm.  long  when  full  grown  (Fig.  152a).  The  pupal 
period  lasts  about  seven  days  under  favorable  conditions. 

Fannia  (Homalomyia)  scalaris  Fab.,  the  latrine  fly,  is  very  similar 
to  the  foregoing.  In  size  the  two  flies  are  about  the  game,  if  anything  the 
latrine  fly  is  somewhat  the  larger.  The  thorax  and  abdomen  are  bluish 
black,  the  antennae  and  palpi  are  black  as  are  the  legs.  The  abdomen 
has  a  dark  median  stripe  which,  with  segmentally  arranged  transverse 
bands  produces  a  series  of  dorsal  triangular  markings.  The  middle  tibia 
is  provided  with  a  distinct  tubercle. 

The  eggs  of  this  fly  are  deposited  on  excrement  of  humans,  horses, 
cows,  etc.,  also  on  decaying  vegetable  matter.     The  egg  stage  lasts 

about  twenty-four  hours,  the  larval 
stage  about  six  days  and  over,  and 
the  pupal  stage  about  nine  days. 

While  the  larva  of  the  "  latrine 
fly  "  resembles  the  larva  of  the  lesser 
house  fly  in  general,  it  is  readily  dis- 
tinguished. The  single  lateral  pro- 
tuberances are  distinctly  feathered 
(Fig.  1526). 

Anthomyia  radicum  Linn,  the  root 
maggot  fly  of  Europe,  is  described 
by  Meade,  according  to  Slingerland  ^ 
viz. :  "It  may  be  recognized  by  its 
projecting  face ;  by  the  scales  of  the 
base  of  the  wings  being  unequal  in 
size  ;  by  the  thorax  being  black  and 
marked  in  the  male  by  two  short, 
gray,  narrow  stripes ;  by  the  rather 
short,  wide,  somewhat  pointed 
abdomen,  with  a  longitudinal  dorsal  black  mark,  crossed  by  three 
transverse  straight  black  stripes  extending  of  an  equal  width  to  the 
margins ;  and  by  the  third  and  fourth  longitudinal  veins  of  the  wings 
being  slightly  convergent  at  their  extremities.     This  inequality  in  the 


Fig.  152.  —  (a)  Larva  of  Fannia  (Ho- 
malomyia) canicularis;  (b)  Larva  of 
Fannia  {Homalomyia)  scalaris.  (Re- 
drawn and  adapted  after  Hewitt.)      X  6. 


1  Slingerland,  M.  V.,  1894.  The  cabbage  root  maggot,  with  notes  on  the 
onion  maggot  and  allied  insects.  Cornell  University  Agr.  Exp.  Sta.,  Bull. 
No.  78,  pp.  481-577. 


MYIASIS  243 

size  of  the  alular  scales,  the  shape  of  the  abdomen,  the  markings  on 
the  body,  and  the  convergence  of  the  third  and  fourth  longitudinal 
veins  of  the  wings  are  characters,  any  one  of  which  woukl  distinguish 
the  male  fly,  at  least,  from  the  cabbage  fly  "  (Phorbia  brassiccc,  Bouche). 

Anthomyia  radicimi  is  a  typical  root  maggot  fly,  its  larvae  developing 
in  the  roots  of  radishes  and  other  plants ;  Bouche  records  the  maggots 
as  developing  in  human  excrement.  According  to  Slingerland  {he. 
cit.)  this  author  gives  eight  to  ten  days  as  the  period  required  to 
pass  through  the  egg  and  larval  stage  and  two  or  three  weeks  for  the 
pupal  stage.  Hewitt  {loc.  cit.)  gives  the  egg  stage  at  from  eighteen  to 
thirty-six  hours,  the  larval  stage  at  about  eight  days  and  the  pupal 
stage  about  ten  days. 

The  fully  grown  larva  measures  "  8  mm.  in  length  and  may  be  dis- 
tinguished by  the  six  pairs  of  spinous  tubercles  surrounding  the  posterior 
end  and  a  seventh  pair  situated  on  the  ventral  surface  posterior  to  the 
anus.  The  tubercles  of  the  sixth  pair,  counting  from  the  dorsal  side, 
are  smaller  than  the  rest  and  are  bifid  "  (Hewitt).  The  ingestion  of 
the  larva  with  uncooked  vegetables  not  thoroughly  masticated,  seems 
to  be  the  mode  of  infection. 

Relation  to  Gastric  and  Intestinal  Myiasis.  —  Many  cases  of  intesti- 
nal myiasis  traceable  to  Anthomyid  flies  are  recorded.  (See  Parasitology, 
Vol.  5,  No.  3,  pp.  161-174.)  "  The  presence  of  these  larvae  in  the  stomach 
is  usually  indicated  by  nausea,  vertigo  and  violent  pains;  the  larvae 
in  many  cases  are  expelled  by  vomiting.  If  they  occur  in  the  intestine, 
they  are  expelled  with  the  feces  and  their  presence  is  signalized  by  diar- 
rheal symptoms,  abdominal  pains  or  haemorrhage  caused  by  the  trau- 
matic lesions  of  the  mucous  membrane  of  the  intestine  which  the  larvae 
aftect"  (Hewitt). 

Mode  of  Infection.  —  As  has  already  been  explained,  the  eggs  of  these 
flies  may  be  deposited  upon_  decaying  or  even  fresh  vegetable  matter 
or  excrement,  in  which  the  larvae  develop.  It  seems  quite  probable  that 
the  young  larvae  (possibly  also  the  eggs)  are  taken  into  the  stomach  in 
uncooked  food.  It  is  also  suggested  (Hewitt)  that  the  flies  may  deposit 
their  eggs  in  or  near  the  anus,  particularly  in  the  use  of  old-fashioned 
open  privies.  The  larva?  on  hatching  are  believed  to  make  their  way  into 
the  intestine. 

Larvae  in  the  Urinary  Tract.  —  Infestation  of  the  urinary  tract  by 
larvae  of  Fannia  canicularis  is  by  no  means  uncommon  according  to 
Chevril.^  The  expulsion  of  larvae  W'ith  the  urine  in  both  sexes  has  been 
recorded.  Entrance  into  the  urinary  tract  is  undoubtedly  gained  by 
the  larvae  through  the  genital  openings  (of  females  primarily),  to  which 
the  adult  flies  have  been  attracted  by  secretions  on  exposure  of  these 
parts  during  sleep  or  drunken  stupor. 

1  Chevril,  R.,  1909.  Sur  la  myase  des  voies  urinairei.  Arch,  de  Parasitol., 
XII,  pp.  369-450. 


244        MEDICAL  AND   VETERINARY  ENTOMOLOGY 


C.   Rat-tailed  Larv^ 

Order  Diptera,  Family  Syrphidos 

Characteristics.  —  The  family  Syrphidse  includes  a  very  large  group 
of  flies,  many  of  which  are  brightly  colored,  varying  greatly  in  size. 
They  are  nearly  all  flower  loving,  feeding  on  nectar  mainly.  Only 
one  genus  needs  be  considered  here,  namely,  Eristalis,  the  larvse  of  which 
have  a  long  anal  breathing  tube,  i.e.  "  rat-tailed,"  and  the  adults  are 
commonly  called  drone  flies. 

Eristalis  tenax,  the  drone  fly  (Fig.  153),  is  a  rather  large  insect, 
somewhat  larger  than  a  honeybee  and  resembles  the  drone  bee  very 

closely,  indeed  is  commonly 
referred  to  as  its  mimic.  The 
fly  deposits  its  eggs  on  liquid 
manure  or  other  filthy  liquids 
in  cans,  slop  jars,  privies,  etc. 
The  larvfe  are  known  as  "  rat- 
tailed  larvae"  (Fig.  154); 
these  also  occur  occasionally 
in  heaps  of  horse  manure. 

Relation  to  Myiasis.  —  The 
frequency  with  which  the  "  rat- 
tailed  "  larvae  occur  in  liquid 
excrement  must  lead  to  ex- 
treme caution  in  accepting  re- 
ports that  these  larvae  have 
been  evacuated  with  discharges 
from  the  bowels.  The  writer 
has  on  several  occasions  re- 
ceived specimens  of  "  rat- 
tailed  "  larvae  which  were  said 
to  have  been  evacuated  bj'  the 
"  double  handful "  and  that 
the  patient  had  "steadily  improved"  thereafter. 

There  are,  however,  several  cases  on  record  which  seem  to  be  in- 
controvertible, notably  the  case  reported  by  Hall  and  Muir,^  who  also 
bring  together  all  recorded  information  to  date  relative  to  Eristalis  and 
myiasis.  The  case  referred  to  was  that  of  a  boy  aged  five  years 
"  who  had  been  ailing  for  about  ten  weeks  and  who  was  under  medical 
treatment  for  indigestion  and  obstinate  constipation  for  about  five 
weeks  of  that  time.  The  child  was  emaciated  and  anemic.  Very 
striking  symptoms  were  the  constant  and  pronounced  twitching  of  the 
eyelids  and  other  nervous  movements.     He  gritted  his  teeth  in  his 

1  Hall,  M.  C,  and  Muir,  J.  T.,  1913.  A  critical  study  of  a  ease  of  myiasis 
due  to  Eristalis.    Archives  of  Intern.  Med.,  Vol.  II,  pp.  193-203. 


Fig.  153.  —  The  drone  fly,  Eristalis  tenax, 
whose  larvae  are  commonly  called  "rat- 
tailed  larvae. "       X  3.5. 


MYIASIS 


245 


sleep  at  times,  and  made  convulsive  movements  of  the  limbs.  When 
awake  he  complained  of  pain  in  the  limbs  and  headache.  The  emaci- 
ation seemed  to  be  due  to  the  fact  that  the  boy  had  for  some  time 
vomited  almost  everything  he  ate.  The 
breath  was  very  bad, '  worse  than  rotten  eggs  ' 
according  to  his  parents.  On  the  basis  of 
the  nervous  and  digestive  disturbance  and 
the  general  debility,  a  diagnosis  of  worm  in- 
festation was  made." 

With  this  diagnosis  in  mind  the  mother 
of  the  boy  gave  him  a  dose  of  a  proprietary 
worm  remedy,  resulting  in  the  discharge  of 
an  object  wriggling  around  vigorously  in  the 
feces  and  urine.  The  slop  jar  into  which 
the  stool  was  passed  was  in  regular  use  and 
had  been  previously  rinsed  with  tap  water 
and  allowed  to  dry  during  the  day.  The 
specimen  was  identified  by  the  authors  as  one 
of  the  "rat- tailed  larvae  "  measuring  3.2  cm. 
in  length,  including  the  long  "  tail."  A 
second  larva  was  said  to  have  been  dis- 
charged the  following  day.  The  case  is  be- 
lieved by  the  authors  to  be  probably  a 
genuine  case  of  "  gastric  myiasis." 

After  the  passage  of  the  larvae  the  child  is 
said  to  have  improved  in  health  and  became 
normal,  the  nervous  symptoms  and  vomiting 
disappeared. 

Three  chances  for  infection  were  pointed  out ;  namely,  first,  the  eating 
of  "overripe"  or  probably  decaying  peaches  in  which  "rat-tailed" 
larvae  might  have  occurred ;  or,  secondly,  to  the  drinking  of  "  ditch  " 
water  polluted  with  kitchen  refuse,  etc. ;  or,  lastly,  to  stable  manure  in 
a  neighbor's  yard  where  the  child  played. 

The  authors  offer  the  following  comment  relative  to  the  gastric  dis- 
turbances : 

"A  larva  supplied  with  the  stigmatic  apparatus  of  Eristalis  would  apparently 
be  fitted  for  hfe  in  a  stomach  with  a  small  amount  of  food  and  plenty  of  the 
atmospheric  air  which  is  swallowed  in  eating  and  drinking  and  at  other  times. 
Such  a  condition  would  simulate  the  normal  life  conditions  fairly  closely. 
That  the  stomach  would  not  fill  to  the  point  where  it  would  drown  the  larva 
might  be  insured  by  the  vomiting,  perhaps  automatically,  the  activity  of  the 
larva  increasing  as  1he  stomach  filled  to  where  it  threatened  to  cover  the  rising 
stigmatic  tube,  and  so  setting  up  an  irritation  leading  to  vomiting.  The 
mother  states  that  the  child's  stomach  was  extremely  intolerant  of  millc  and 
that  drinking  milk  was  promptly  followed  by  vomiting.  This  suggests  that 
milk,  usually  taken  in  long  drinks  and  considerable  quantities,  quickly  threat- 
ened the  larva  with  drowning  and  set  up  such  activity  as  promptly  to  cause 
vomiting." 


Fig.  154.  —  The  "rat-tailed 
larva"  of  Eristalis  tenax, 
drone  fly.       X  2. 


246       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


D.   Botflies 
Order  Diptera,  Family  CEstridcB 

Characteristics  of  the  (Estridae.  —  The  CEstridse  are  described  by 
Williston  as  follows:  "  Flies  of  moderate  to  rather  large  size,  thick- 
set, usually  more  or  less  pilose.  Head  large,  the  lower  part  more  or  less 
swollen.  Antennae  short,  three-jointed,  decumbent,  and  more  or  less 
sunken  in  the  facial  groove  or  grooves ;  arista  bare  or  plumose.  Mouth 
opening  small,  the  mouth  parts  sometimes  rudimentary,  never  large. 
Front  broad  in  both  sexes,  in  the  male  broader  in  front.  Eyes  compara- 
tively small,  bare.  Ocelli  present.  Thorax  robust,  with  a  distinct  trans- 
verse suture.  Abdomen  short,  conical  or  but  little  elongated  ;  genitalia  of 
the  male  hidden,  the  ovipositor  sometimes  elongated.  Legs  moderately 
long,  the  hind  pair  sometimes  elongated.  Tegulie  usually  large  ;  some- 
times small.  Xeuration  of  the  w^ngs  muscid-like,  in  most  cases  the 
first  posterior  cell  narrowed  or  closed  ;  anal  cell  small,  usually  indistinct ; 
discal  cell  sometimes  absent. 

"  This  family,  though  of  small  size  comparatively,  is  of  the  greatest 
interest  by  reason  of  the  habits  of  the  larvse,  all  of  which  that  are  known 
are  parasitic  upon  mammals.  The  adult  flies  often  have  rudimentary 
mouth  parts,  and  devote  the  whole  of  their  brief  existence  to  the  labors 
of  procreation.  .  .  .  Parasitism  occurs  in  three  principal  ways,  in  the 
stomach  and  digestive  tubes,  in  tumors  formed  by  the  larvae  under  the 
skin  and  in  the  pharyngeal  and  nasal  cavities.  With  but  few  excep- 
tions each  species  is  confined  to  a  single  species  of  mammal,  and  each 
genus  or  each  group  of  allied  species  is  parasitic  in  the  same  way  upon 
similar  animals." 

a.   Horse  Boh 

Characteristics.  —  GastrophUm  equi  Fabr.  is  the  common  horse  bot 
(Fi^.  155).     This  species  is  des?ribei  by  Osborn,  viz.,  "Adults  of  this 


Fig.  155.  —  The  home  hoi^y,  Gastrophilus  cqui.     (Female,  left ;  male,  right.)       X  1.6. 

species  are  about  18  mm.  in  length,  the  wings  are  transparent  with 
dark  spots,   those    near  the   center    forming    an  irregular  transverse 


MYIASIS 


247 


band.  The  body  is  very  hairy,  the  head  brown  with  whitish  front, 
thorax  brown,  abdomen  brown  with  three  rows  of  blackish  spots, 
which  are  subject  to  considerable  variations.  In  the 
females  the  segments  are  often  almost  entirely  brown 
with  simply  a  marginal  series  of  yellowish  spots,  while 
in  the  males  the  abdomen  may  be  almost  entirely  yellow 
or  very  light  brown,  with  brown  or  dark  brown  spots 
very  distinct.  The  males  are  rarely  seen,  for  while 
it  is  one  of  the  most  common  occurrences  to  witness 
the  females  around  the  horses  depositing  their  eggs, 
the  males  evidently  hold  aloof.  They  are  readily  dis- 
tinguished by  the  form  of  the  abdomen,  which  lacks 
the  two  tubular  segments  at  the  end,  and  is  provided 
on  the  under  side  of  the  last  segment  with  a  pair  of 
dark  brown  or  black  hooks,  or  clasping  organs.  Other- 
wise, except  the  color  of  the  abdomen,  already  men- 
tioned, they  resemble  very  closely  the  females." 

Life  History. — ^  The  eggs  (Fig.  156),  which  are  light  I'lo.  1 56.  —  Eggs 
yellow,  are  attached  to  the  hairs  of  the  forelegs,  belly,  fly,  attaciied  to 
shoulders  and  other  parts  of  the  body.  The  female  j^  ^^^^  ^in^^^ 
fly  may  be  seen  hovering  two  or  three  feet  away  from 
the  horse,  and  suddenly  is  seen  to  dart  at  the  animal,  fastening  an 
egg  firmly  in  place.  This  process  is  repeated  until  perhaps  several 
hundred  eggs  may  be  attached.  The  very  careful 
observations  of  Osborn  (and  corroborated  in  the 
main  by  the  writer)  indicate  that  "  the  eggs 
normally  require  friction  and  moisture  to  permit  of 
their  hatching  and  transfer  to  the  horse's  mouth, 
that  hatching  occurs  with  difficulty  before  the  tenth 
day,  and  most  readily  after  the  fourteenth  day,  and 
that  they  lose  vitality  at  a  period  varying  between 
the  twenty-eighth  and  fortieth  days,  the  bulk  not 
surviving  more  than  four  weeks."  The  newly 
hatched  larva  is  a  very  spiny  creature  (Fig.  157) 
which  readily  adheres  to  moist  surfaces,  hence  must 
easily  adhere  to  the  rough,  moist  tongue  of  the  horse, 
passing  into  the  mouth  and  gradually  working  its 
way  down  the  esophagus  to  the  stomach,  where  it 
attaches  itself  to  the  mucous  lining  by  means  of  the 
strong  oral  booklets.  The  stomach  wall  often  be- 
comes so  crowded  with  bots  that  there  is  hardly 
room  for  a  finger  to  touch  the  stomach  without 
coming  in  contact  with  bots  (Fig.  158). 

The  bots  remain  attached,  growling  slowly 
throughout  the  rest  of  the  summer,  autumn  and  winter,  until  late 
spring,  when  full  growth  is  reached,  having  molted  twice  during  this 


Fig.  157.  —  Newly 
emerged  larva  of 
the  horse  botfly. 
X  60. 


248       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


time.  They  are  then  from  L5-2  em.  long  (Fig.  159).  At  this  time  the 
insects  let  go,  gradually  pass  out  through  the  intestine  with  the  feces 
and  drop  to  the  ground.  Reaching  the  ground,  the  bots  burrow  into 
loose  earth  and  in  a  few  days  pupate.  The  pupal  period  varies  con- 
siderably, depending  upon  moisture  and  temperature  conditions,  but  the 
usual  time  is  from  three  to  five  weeks,  when  the  winged  flies  emerge. 
Copulation  takes  place  soon,  inasmuch  as  the  insects  probably  partake 


Fig.  158. 


■  Horse  bots  (Gastrophilus  equi)  attached  to  inner  lining  of  the  stomach 
of  a  horse.      (Photo  by  Wherry.)      X  .75. 


of  little  or  no  food;  egg  laying  begins  again  in  early  summer,  and  as 
new  individuals  emerge  continues  until  autumn. 

Pathogenesis.  —  While  a  moderate  infestation  of  bots  will  give  no 
outward  indications,  a  heavy  infestation  will  be  indicated  by  digestive 
disorders  (which  may  of  course  be  traceable  to  other  causes  as  well). 
The  discovery  of  bots  in  the  manure  is  sufficient  evidence.  A  light  in- 
festation is  probably  of  no  consequence,  —  there  are  indeed  some  indi- 
viduals who  erroneously  maintain  that  a  horse  must  have  at  least  a  few 
bots  in  order  to  be  well. 


MYIASIS 


249 


The  injury  which  bots  produce  is,  first,  abstraction  of  nutriment, 
both  from  the  stomach  and  its  contents  ;  second,  obstruction  to  the  food 
passing  from  the  stomach  to  the  intestine,  particularly  when  the  larvae 
are  in  or  near  the  pylorus ;  third,  irritation  and  injury  to  the  mucous 
membrane  of  the  stomach  due  to  the  penetration  of  the  oral  booklets ; 
fourth,  irritation  of  the  intestine,  rectum  and  anus  in  passage. 

Treatment.  —  Internal  remedies  are  always  best  and  most  safely  ad- 
ministered by  a  veterinarian.  However,  turpentine  is  commonly  used 
in  four-ounce  doses,  four  hours  apart,  until  three  or  four  doses  have  been 
administered.  It  is  recommended  that  the  last  dose  be  followed  by  one 
ounce  of  powdered  aloes.  The  use  of  turpentine  is  dangerous  unless 
it  is  given  by  an  experienced  person. 
Washburn  ^  states  that  carbon  bisulphide 
has  been  used  in  Italy  with  marked  success. 
Six  gelatine  capsules,  each  containing  15 
grains  of  CS2,  were  given  to  two  horses  at 
intervals  of  two  hours.  During  the  four 
following  days  the  first  horse  passed  497  bots, 
the  second  in  five  days,  571  bots.  Another 
party  gave  one  horse  32  grains  in  five  hours, 
and  the  animal  passed  203  bots.  Horses  so 
treated  should  be  carefully  watched,  and  if 
any  bad  effects  appear,  treatment  should  be 
stopped. 

Prevention.  —  The  object  in  view  is  to 
prevent  the  botfly  larvae  from  gaining  en- 
trance to  the  mouth  of  the  horse,  hence 
control  methods  involve  the  egg.  The  first 
method  that  presents  itself  is  to  prevent  the 
fly  from  depositing  its  eggs  on  the  horse. 
This  can  be  done  by  keeping  the  animals 
stabled  during  the  day,  giving  them  free 
range  at  night. 

A  second  method  involves  the  destruction  or  removal  of  the  eggs 
from  the  horse.  Touching  the  eggs  lightly  with  kerosene,  benzine  or 
gasoline  proves  effective.  The  eggs  are  easily  removed  with  a  sharp 
razor  or  clippers,  in  which  case  treatment  is  unnecessary. 

Based  on  our  knowledge  of  the  egg  stage  it  would  seem  that  very 
few  bots  would  reach  the  stomach  of  the  horse  if  the  animal  is  treated 
as  above  at  least  once  every  two  weeks. 

If  internal  remedies  are  administered  and  the  bots  are  full  grown 
or  nearly  so.  it  is  safer  to  treat  the  manure  copiously  with  kerosene, 
carbolic  acid  or  sheep  dip  in  order  to  destroy  the  larvae  to  prevent 
pupation  and  emergence  of  the  flies. 

Other  Species  of  Horse  Bots. — Gastrophilus  hcBmorrhoidalis  Linn,  is 

»  Washburn,  F.  L.,  1905  {loc.  ciL). 


Fig.  159.  —  Larva  of  Gastro- 
philus  egui,  the  horse  hot. 
X4. 


250       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

the  red-tailed  bot.  This  species  is  about  1.5  cm .  in  length  with  an  orange- 
red-tipped  abdomen.  "  The  thorax  is  olive-gray  and  hairy,  with  a  black 
band  behind  the  suture.  The  base  of  the  abdomen  is  whitish  and  the 
middle  blackish,  in  strange  contrast  with  the  orange-red  of  the  end." 
The  eggs  of  this  species  are  dark  brown  to  nearly  black  and  are  deposited 
on  the  long  hairs  of  the  horse's  lip.  The  incubation  period  is  very  much 
shorter  than  in  G.  equi.  The  larvse  find  their  way  into  the  mouth  on 
food  or  with  the  tongue  in  licking,  and  eventually  reach  the  stomach. 
The  fully  grown  larvae  are  from  12  to  15  mm.  long.  Law  describes 
the  larvse,  viz. :  "  The  spines  are  arranged  in  a  double  row  on  each  ring, 
but  on  the  dorsal  aspect  they  are  absent  in  the  middle  of  the  ninth  ring, 
while  on  the  tenth  and  eleventh  there  are  none.  The  larvte  pass  the 
winter  mostly  attached  in  groups  in  the  left  sac  of  the  stomach,  but  also 
in  the  right  sac,  and  duodenum,  and  exceptionally  in  the  pharynx." 

"  When  mature  and  passing  out  through  the  intestines  they  often 
hook  themselves  for  a  time  to  the  rectal  mucosa,  wdiere  they  cause  con- 
siderable irritation  and  rubbing  of  the  tail.  They  also  pass  through  the 
anus  independently  of  defecation,  and  hook  themselves  to  the  skin 
round  its  outer  margin,  causing  rubbing  and  switching  of  the  tail,  and  a 
StiflF  awkward  gait.  This  habit,  with  that  of  laying  the  eggs  on  the  lips 
and  jaw,  and  of  hooking  on  the  delicate  mucosae  of  the  pharynx,  right 
gastric  sac  and  duodenum,  renders  tliis  one  of  the  most  injurious  of  the 
(Estridse"  (Osborn). 

The  pupal  stage  is  entered  soon  after  the  bot  drops  to  the  ground 
and  buries  itself,  and  lasts  from  four  to  six  weeks  and  over.  The  flies 
occur  from  early  summer  to  late  autumn. 

Gastrophilus  nasalis  Linn,  is  the  chin  fly,  which  measures  about 
1  cm,  in  length.  It  is  "  densely  hairy,  with  the  thorax  yellowish  red 
or  rust  colored.  The  abdomen  is  either  whitish  at  the  base,  with  the 
middle  black  and  the  apex  yellowish  brown  and  hairy,  or  the  base  is 
whitish  and  all  the  rest  brown ;  or  the  middle  is  black ;  with  the  base 
and  apex  whitish,  with  gravish  hairs.  The  wings  are  unspotted  "  (Ver- 
rill). 

The  white  eggs  are  deposited  on  the  lips  or  around  the  nostrils.  The 
larvae  are  "  furnished  with  a  row  of  spines  on  each  ring  from  the  second 
to  the  ninth  on  the  dorsal  surface,  and  as  far  as  the  tenth  on  the  ventral. 
There  is  an  unarmed  part  in  the  center  of  the  eighth  and  ninth  rings  on 
the  dorsal  surface.  It  spends  the  winter  attached  to  the  mucosa  of  the 
commencement  of  the  duodenum,  usually  in  clusters,  and  is  rarely  found 
in  the  stomach.  In  passing  out  it  shows  no  tendency  to  hook  itself  to 
other  parts  of  the  intestine  or  the  anus  "  (Law). 

The  remainder  of  the  life  history  is  as  in  other  species  already  de- 
scribed. 

Gastrophilus  pecorum  Fabr.  is  about  the  same  size  as  G.  equi. 
In  color  it  is  yellowish  brown  to  nearly  black.  The  wings  are  brownish 
and  clouded.     In  egg  deposition,  life  history  and  habits  this  species  re- 


MYIASIS 


251 


sembles  (I.  cqui  very  closely.     It  is  said  to  be  rare  or  absent  in  the 
United  States. 

b.  Ox  Warbles 

Characteristics.  —  Ilypoderma  lineata  Villers  is  the  common  ox 
warble  fly  (Fig.  160),  also  known  as  the  "  heel  fly,"  which,  together 
with  a  less  prevalent  species,  //.  bovis  De  G.,  is  responsible  for  the 
warble  or  grub  in  cattle.  This  species  is  described  as  follows : 
"Length,  13  mm.  (15  mm.  with  ovipositor  extended);  general  color, 
black ;  body  more  or  less  clothed  with  yellowish  white,  reddish  and 
brownish  black  hairs.  The  front,  sides,  and  back  of  the  head,  the 
sides  of  the  thorax,  a  band  across  the  base  of  the  scutellum,  and 
the  basal  segment  of  the  abdomen  are  covered  with  long  yellowish 
white,  almost  white,  hairs.  The  head  above,  central  thoracic  region, 
including  prothorax  and  mesothorax,  middle  segments  of  the  ab- 
domen above,  and  legs,  clothed  with  brownish 
black  hairs,  which  on  the  head  and  thorax 
are  more  or  less  intermixed  with  whitish 
hairs.  The  covering  of  hairs  is  shorter  and 
scantier  on  the  head  and  thorax,  and  the  tip 
of  the  scutellum  and  following  parts  of  the 
thorax,  together  with  four  prominent  lines 
on  the  thorax,  smooth  and  highly  polished. 
The  hairs  of  the  terminal  segments  of  the 
abdomen  are  reddish  orange,  which  color 
also  predominates  on  the  hind  tibise." 

Life  History  and  Habits.  —  The  female 
deposits  her  eggs  on  the  feet,  legs,  flanks, 
belly  and  other  parts  of  the  body.  The  eggs 
are  white,  about  1  mm.  long,  and  are  securely 
attached  in  rows  of  six,  more  or  less,  on  a 
single  hair.  Deposition  occurs  from  early 
summer  to  late  autumn.  The  larvae  hatch 
in  a  week  more  or  less,  protruding  the  body 
from  the  egg  or  crawling  out  and  clinging  to 
the  hairs  of  the  host,  when  they  are  licked  oft' 
with  the  tongue,  pass  into  the  mouth,  thence  into  the  esophagus,  and 
often  into  the  paunch.  Once  in  the  esophagus  or  paunch  the  larvae 
burrow,  finding  their  way  into  the  tissue  between  the  mucous  mem- 
brane and  the  muscular  coat  of  these  organs.  In  this  region  the 
smooth  yellowish  white  larvae  remain  for  the  rest  of  the  summer  and 
autumn  and  grow  to  be  from  12  to  15  mm.  in  length.  During  the  late 
autumn  and  winter  the  still  smooth  larvae  begin  to  penetrate  the  muscu- 
lar coat  of  the  esophagus,  entering  the  connective  tissue  of  the  abdominal 
cavity  and  dorsal  muscles,  continuing  their  migration  toward  the  back 
of  the  host.     The  large  warble  {Eypoderma  bovis)  is  said  to  often  enter 


Fig.   160.  —  The  ox  warble  fly, 
Hypoderma  lineata.       X  2.6. 


252       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


the  spinal  canal  through  the  intervertebral  foramina,  remaining  there 
for  two  or  three  months  and  leaving  this  location  by  the  same  path  which 
was  followed  on  entering,  and  soon  find  their  way  to  their  ultimate  posi- 
tion in  the  host  in  the  subcutaneous  connective  tissue  beneath  the  skin 
of  the  back.     Larvae  are  also  known  to  enter  the  skin  directly. 

About  the  latter  part  of  December  (the  writer  has  observed  them 
about  Christmas  time)  there  appear  the  small  swellings  along  the  back 
(near  the  spinal  column)  of  the  cattle.  These  lumps  it  will  be  noted 
change  in  position  from  day  to  day,  appearing  on  the  shoulders,  sides  and 
rump  as  well.  Soon  the  lumps  become  stationary  and  there  appears  a 
small  opening  in  the  middle  of  the  elevated  area  through  which  the  grub 
receives  oxygen,  having  its  posterior  end  close  to  this  hole.  The  skin  is 
again  shed  (the  third  and  last  molt)  and  the  larva  now  appears  as  a 
thick  heavy  set  spiny  maggot  about  ^  cm.  in  length  (Fig.  161).  The 
tumor  increases  to  the  size  of  a  walnut,  the  aperture  becomes  larger  and 
in  early  to  late  spring  the  grub  crawls  out,  falls  to  the  ground,  burrows 
into  loose  earth  and  in  a  day  or  two  pupates. 
The  pupa  is  about  2  cm.  long,  dark  brown  to 
black  in  color.  The  winged  insect  emerges  from 
the  pupa  case  in  from  three  to  five  weeks  and 


over. 


Fig.  161. — Larva  or  grub 
of  the  ox  warble  fly, 
H  ypoderma  lineata. 
X  1.3. 


H ypoderma  bovis  De  G.  is  commonly  called 
the  European  or  larger  warble  fly.  This  species 
is  now  known  to  occur  in  British  Columbia.  In 
Europe,  H.  Bovis  predominates  over  H.  lineata. 
It  is  about  15  mm.  in  length  against  13  mm.  in 
the  latter.  Both  species  are  hairy,  resembling 
bees,  the  ground  color  is  black  with  long  hairs 
on  the  front,  sides  and  back  of  the  head,  sides 
of  thorax  and  base  of  abdomen.  In  H.  bovis 
these  hairs  are  greenish  yellow.  The  tip  of  the 
abdomen  in  both  species  is  reddish  yellow, 
deeper  and  more  hairy  in  H.  bovis. 

The  life  history  of  the  two  species  is  very 
similar.  The  larvae  are  different  enough  to  distinguish  them  readily. 
The  fully  grown  larva  of  H.  bovis  is  longer,  27-28  mm.,  H.  lineata 
about  25  mm.  The  two  species  are  distinguished  on  the  basis  of  their 
spiny  armature.  In  H.  lineata  each  segment  of  the  larva  is  provided 
with  spines  except  the  last,  the  ring  upon  which  the  stigmata  are 
located,  while  in  //.  bovis  all  except  the  last  two  are  armored. 

Injury  Done.  —  The  injury  done  by  the  warbles  is  first  that  of  irritation 
caused  by  their  migrations  in  the  body  of  the  animal  and  later  in  their 
emergence  from  beneath  the  skin ;  secondly,  the  escape  of  the  larva  from 
the  tumor  leaves  an  open,  running  wound  which  persists  for  a  long  time 
and  is  attractive  to  screw  worm  flies  and  other  tormenting  insects.  The 
direct  pathogenesis  is  of  minor  importance,  however,  in  the  face  of  the 
economic  loss  produced  by  this  insect. 


MYIASIS 


253 


Economic  Losses.  —  The  economic  losses  produced  are  first,  reduc- 
tion in  milk  secretion,  which  is  estimated  at  from  10  to  20  per  cent  of  the 
normal  yield ;  second,  loss  of  flesh  due  to  the  wild  endeavor  of  the  ani- 
mals to  escape  from  the  flies  and  the  irritating  larvae  (which  is  pointed 
out  by  Holstein,  viz. :  "  A  cow  quietly  grazing  will  suddenly  spring  for- 
ward, throw  up  her  tail,  and  make  for  the  nearest  water  at  a  headtong 
gait.     Seemingly  deprived  at  the  moment  of  every  instinct  except  the 


Fig.  162. 


-A  piece  of  sole  leather  (Grubby  Jumbo),  21  X  31.5  cm.  showing  work  of 
ox  warble.      X  3. 


desire  to  escape,  she  will  rush  over  a  high  bluff  on  the  way,  often  being 
killed  by  the  fall.  This,  with  miring  in  water  holes  and  the  fact  that 
cattle  are  prevented  from  feeding,  causes  the  loss") ;  third,  depreciation 
of  the  value  of  the  carcass  as  flesh,  which  becomes  greenish  yellow  and 
jelly-like  in  appearance  at  the  points  where  the  grubs  are  located,  and  is 
not  fit  for  consumption ;  fourth,  injury  produced  to  the  hide  which  be- 
comes '  grubby,'  full  of  holes  where  the  grubs  have  emerged  (Fig.  162). 
The  following  is  quoted  from  Tanners'  Work  for  October,  1913 : 
"  The  case  is  recorded  by  Boas  of  Denmark  of  a  cow  which  remained  in 
poor  condition  and  gave  33  pounds  of  milk  per  day.  Forty-six  grubs 
were  extracted  from  this  animal  and  eight  days  later  she  was  giving  44 
pounds  of  milk  per  day,  continued  to  do  so  most  of  the  summer  and  was 
in  good  flesh  and  condition  in  the  fall.  In  this  case  the  loss  of  milk  due 
to  the  grub  infestation  was  25  per  cent.  The  loss  in  flesh  on  account 
of  grubs  has  been  variously  estimated  at  from  $1.00  to  $5.00  or  more 


254       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

per  head.  If  we  assume  that  25  per  cent  of  all  of  the  cattle  in  the  United 
States  are  more  or  less  infested  with  grubs,  a  quite  conservative  estimate, 
50  per  cent  probably  being  nearer  the  actual  percentage,  the  loss  in  flesh 
on  account  of  grubs  amounts  to  from  §15,000,000  to  $75,000,000  a  year, 
the  total  number  of  cattle  in  the  Ignited  States  being  calculated  as  ap- 
proximately 60,000,000.  If  we  also  assume  that  infested  milch  cows 
lose  10  per  cent  in  milk  production  and  that  25  per  cent  of  the  20,000,000 
milch  cows  in  the  United  States  are  affected,  there  should  be  added  to  the 
account  a  loss  of  not  less  than  $30,000,000  per  year. 

"  As  to  the  loss  in  hides  it  is  stated  byEuropean  tanners  that  a  grubby 
hide  is,  on  the  average,  less  in  value  by  one  third  than  a  perfect  hide, 
but  for  this  country,  I  have  no  definite  information  other  than  that 
grubby  hides  in  the  green  state  are  commonly  valued  at  1  cent  a  pound  less 
than  perfect  hides.  On  this  basis  the  depreciation  in  value  of  a  hide  of 
average  weight  of  65  pounds  if  grub-infested,  would  be  65  cents  and  the 
depreciation  in  the  value  of  the  estimated  15,000,000  grubby  cattle  of 
the  United  States  so  far  as  their  hides  are  concerned  thus  amounts  to 
$9,750,000.  It  is,  however,  quite  probable  that  the  actual  loss  in  the 
value  of  hides  when  made  into  leather  is  much  greater  than  this, 

"  Without  including  the  loss  on  account  of  the  direct  damage  to  beef 
carcasses  from  the  presence  of  grubs,  we  may,  on  the  basis  of  the  forego- 
ing, estimate  the  total  loss  from  grubs  in  the  United  States  in  round  num- 
bers at  from  $55,000,000  to  $120,000,000  per  year." 

Treatment.  —  The  tumors  in  which  the  grubs  occur  may  be  treated 
with  kerosene,  benzine,  turpentine  or  carbolic  acid,  a  few  drops  of  which 
are  introduced  into  the  opening  by  means  of  a  machinist's  oiler,  or  merely 
smeared  over  the  surface.  Ointment  of  sulphur  and  vaseline  are  also 
serviceable.  These  remedies  are  objectionable  inasmuch  as  the  grubs 
are  not  eliminated,  dying  within  the  tumor  where  they  must  be  slowly 
absorbed  ;   serious  abscesses  may  result. 

The  grubs  may  also  be  destroyed  in  situ  with  a  sharp  scalpel  or  a  hot 
needle,  but  here  again  the  same  objection  as  above  is  encountered. 

A  better  method  is  to  remove  the  grubs  bodily,  which  can  easily  be 
done  by  squeezing  them  out  if  the  grubs  are  about  ready  to  leave  the 
tumor.  If  not  easily  squeezed  out,  a  forceps  with  slender  blades  may  be 
introduced  into  the  opening,  the  grub  grasped  and  eliminated.  In  some 
cases  the  use  of  a  lancet  may  be  needed  to  widen  the  opening  in  the 
tumor. 

After  removal  the  grubs  must  be  destroyed  to  prevent  further 
metamorphosis,  and  the  wound  should  be  treated  with  a  carbolated 
salve. 

Prevention.  —  Owing  to  the  fact  that  the  eggs  hatch  very  soon  after 
deposition,  treatment  with  kerosene,  benzine  or  gasoline  would  have  to 
be  given  as  soon  as  the  eggs  are  noticed.  This  treatment  is  not  particu- 
larly practical  but  is  not  to  be  disregarded. 

Removal  of  the  grubs  or  treatment  of  the  same  prevents  the  comple- 


MYIASIS 


255 


tion  of  metamorphosis  and  hence  results  in  the  re(kiction  of  the  number 
of  adult  flies  for  the  next  season. 

Associations  for  the  eradication  of  grubs  have  been  formed  in  Europe, 
which  cope  with  the  problem  through  educational  methods.  In  some 
districts  a  bounty  is  offered  from  |  cent  to  f  cent  per  grub.  Their  efforts 
have  given  very  good  results.  Xo  practical  method  of  eradication  in 
range  animals  is  at  hand,  but  certainly  there  is  no  reason  why  with  proper 
cooperation  and  systematic  effort  this  evil  could  not  be  controlled  where 
only  smaller  herds  are  concerned,  thus  actually  saving  large  sums  of 
money  to  the  stock  raiser  and  dairyman. 


Fk 


c.   Head  Maggot  of  Sheep 

Characteristics.  —  Oestrus  ovis  Linn,  is  the  botfly  of  sheep,  or  the 
sheep  gadfly,  the  larva  of  which  is  the  common  head  maggot  of  these 
animals.  '  Grub-in-the-head,' 

*  false  gid  '    and   '  staggers  '   are 
common  designations. 

The  fly  (Fig.  163)  is  some- 
what larger  than  the  common 
house  fly,  dull  yellow  or  brown- 
ish in  color  and  hairy.  The 
abdomen  is  variegated  with 
brown  and  straw  yellow,  the  feet 
are  brown.  It  is  further  de- 
scribed by  Osborn  as  follows : 
"  The  under  side  of  the  head  is 
puffed  out  and  white.  The 
antennae  are  extremely  small  and 
spring  from  two  lobes  which  are  sunk  into  a  cavity  at  the  anterior  and 
under  part  of  the  head.  The  eyes  are  purplish  brown,  and  three  small 
eyelets  are  distinctly  visible  on  the  top  of  the  head.  It  has  no  mouth 
and  cannot,  therefore,  take  any  nourishment.  The  wings  are  trans- 
parent and  extend  beyond  the  body,  and  the  winglets  (calypteres)  which 
are  quite  large  and  white,  cover  entirely  the  poisers.  It  is  quite  lazy, 
and,  except  when  attempting  to  deposit  its  eggs,  the  wings  are  seldom 
used." 

Life  History.  —  The  head  maggot  fly  deposits  living  young  from 
early  summer  to  autumn  in  the  nostrils  of  sheep  and  goats.  These 
at  once  begin  to  migrate  up  the  nasal  passages,  working  their  way  up 
into  the  nasal  sinuses  often  as  far  as  the  base  of  the  horns  in  rams 
and  attach  themselves  to  the  mucous  membranes.  Here  numbers  of 
these  whitish  grubs  may  be  found  wedged  in  closely  in  various  condi- 
tions of  development  (see  Fig.  167).  The  posterior  ends  which  are 
unattached  present  conspicuous  spiracles.     The  grubs  (Fig.  164)  reach 


163.  —  Head  maggot  fly  {CEstrus  oris) 
of  sheep.       X  4. 


256       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


full  growth  with  a  length  of  from  25  to  30  mm.  by  the  following  spring, 
—  a  larval  period  of  from  eight  to  ten  months.  At  the  end  of  this 
time  they  let  go,  wriggling  their  way  out  of  the  nostrils,  fall  to  the 
ground,  bury  themselves  in  the  earth  and  pupate  in  a  few  hours.  The 
pupal  period  lasts  from  three  to  six  weeks  and  over. 

Symptoms.  —  In  the  presence  of  the  fly  the  sheep  are  very  much 
excited,  shake  the  head,  rush  with  their  noses  between  their  fellows, 


Fig.  164. — Head  maggot 
(CEstrus  ovis)  of  sheep. 
X2.5. 


Fig.  165.  —  The  larva  of  a  rabbit  botfly, 
Cuterebra  sp.      X  3. 


push  their  noses  into  the  dust,  snort  and  otherwise  indicate  that  they 
are  trying  to  escape  something  that  persists  in  entering  the  nostrils. 
Once  infected  there  is  a  purulent  discharge  from  the  nostrils,  vigorous 
shaking  of  the  head,  and  perhaps  occasional  discharge  of  a  maggot,  loss 
of  appetite,  grating  of  the  teeth,  and  when  the  animal  walks  the  fore 
feet  are  lifted  in  a  pawing  movement. 

The  great  majority  of  the  cases  do  not  result  fatally,  but  death 
often  results  in  a  week  more  or  less  after  the  appearance  of  aggravated 
symptoms. 

Grub-in-the-head  is  distinguished  from  "gid"  (caused  by  a  larval 
tapeworm,  Ccenurus  cerebralis  =  Midticeps  jnidticeps)  in  that  the  former 
is  always  associated  with  purulent  discharges  from  the  nostrils,  absent 
in  the  latter,  and  that  the  symptoms  of  the  former  appear  during  the 
summer,  and  that  the  latter  occurs  ordinarily  in  lambs  and  yearlings 
only  (Law).     There  is  no  undue  sneezing  or  rubbing  of  the  nose  in  gid. 


MYIASIS  257 

Treatment. — Materials  such  as  snuff,  pepper,  etc.,  may  be  in- 
troduced into  the  nostrils  or  sprinkled  among  the  flock,  to  induce  violent 
sneezing,  which  causes  the  expulsion  of  many  of  the  larger  grubs.  Law 
recommends  the  injection  of  benzine,  lifting  the  sheep's  nose  somewhat 
and  pouring  into  the  nostrils  a  teaspoonful  of  the  remedy  for  each 
nostril.  The  lower  nostril  into  which  the  benzine  is  poured  is  held 
shut  for  thirty  seconds;  the  other  side  is  then  turned  and  the  treat- 
ment repeated.  The  application  is  repeated  daily  or  oftener  until  the 
maggots  are  all  expelled. 

Prevention.  —  The  use  of  "  salt  logs  "  in  sheep  pastures  is  made  by 
some  sheep  raisers.  These  logs  are  made  by  boring  two-inch  holes  at 
intervals  of  about  six  inches  along  the  length  on  top.  Salt  is  placed 
into  these  holes,  which  are  kept  about  half  full,  and  in  turn  the  edges 
of  the  holes  are  repeatedly  smeared  with  pine  tar,  or  other  repellent 
material.  In  endeavoring  to  reach  the  salt  the  sheep  involuntarily 
smears  its  nose  with  the  substance,  which  protects  it  to  a  large  extent 
against  the  head  maggot  fly. 


d.  Bots  in  Rodents 

Bots  in  Rodents.  —  Various  species  of  rodents,   notably  rabbits, 
rats  and  squirrels  are  infested  at  times  with  bots  or  perhaps  we  had  better 
say,  warbles  (Fig.  165).     Rabbits,  both  wild  and  tame,  are  commonly 
affected  by  Cuterebra  cuniculi  Clark,  and 
probably  other  species.     C.  cuniculi  is  a 
large   black   and    white   bumblebee-like 
fly  (Fig.  166).     Just  where  the  eggs  are 
deposited  and  how  the  grubs  reach  their 
position  under  the  skin  is  still  unknown. 
After  leaving  the  body  of  the  host  the 
larvae  pupate  in  three  or  four  days,  re- 
maining in  the  pupal  stage  often  for  a  Fig.  166.  — A  rabbit  botfly, 
considerable  period;  one  case   observed 
by  the  writer  pupated  October  25,  1912,  and  emerged  August  12,  1913. 

The  emasculating  bot  (Cuterebra  emasculator  Fitch)  of  squirrels  is 
found  in  the  grub  stage  in  the  scrotum  of  squirrels  of  several  species. 

e.   Head  Maggot  of  Deer 

Head  Maggot  of  Deer.  —  The  black-tailed  deer  {Odocoileus  colum- 
bianus)  and  probably  other  species  as  well  are  commonly  affected  with 
head  maggots,  a  species  of  the  genus  Cephenomyia.  The  attached 
figure  (Fig.  167)  illustrates  the  fact  that  the  larvae  crowd  into  the  si- 
nuses and  that  there  are  all  sizes,  from  very  young  to  fully  grown,  present 
at  the  same  time. 


258       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

/.  Warbles  in   Humans 

Warbles  in  Humans.  —  Humans,  notably  in  Central  and  South 
America,  Mexico  and  other  tropical  countries,  are  rather  commonly 
affected  with  warbles  traceable  to  one  of  several  species  of  QHstrids, 


im 

««e  __^ 

^^B 

j^^ 

%^^^, 

mm 

^s^'jf^'-jp^^ 

L^v'       ^»- 

IK 

mj4 

MM 

t^^^         ^*W 

^'s* 

^"^          i 

g^            1 

Fig.  167. 


Head  maggots,  larvce  of  Cephenotnyia  sp.  attached  to  tissue  in  nasal 
sinuses  of  the  deer.       X  .6. 


notably  Dermatobia  hominis  Gmelin  =  Dehnatobia  noxialis  Guodot  = 
Dermatobia  cyaniventris  MacQ.,  Hypoder ma  lineata,  Vill.,  and  H.  bovis, 
DeG. 

Dermatobia  hominis  Gmelin  ^  is  commonly  found  in  Central  and 
South  America  and  Mexico.  The  larva  is  known  in  its  early  stage  as 
Ver  macaque  and  in  its  later  stages  as  torcel  or  berne.  The  fly  measures 
from  14  to  16  mm.  in  length,  is  entirely  brown  in  color.  This  fly  para- 
sitizes a  large  number  of  species  of  mammals  and  even  birds.  It  has 
been  found  in  cattle,  pigs,  dogs,  mules,  monkeys,  man  and  various  wild 
animals.  In  man  the  larva  "  has  been  reported  from  various  regions 
of  the  body,  mainly  head,  arm,  back,  abdomen,  scrotum,  buttocks,  thigh 
and  axilla." 

Whether  the  fly  introduces  the  egg  under  the  skin  of  its  host  by  means 
of  the  ovipositor  is  unknown  but  in  certain  recorded  cases  there  is  a  his- 
tory of  a  sting.  According  to  some  authors  the  larval  period  requires 
about  three  months  when  the  insect  leaves  the  flesh,  drops  to  the  ground 
and  pupates,  the  pupal  period  requiring  about  six  weeks. 

Pathogenesis.  —  The  following  is  quoted  from  Ward  (he.  cit.) : 
"  Dr.  Brick  was  stung  by  some  insect  while  bathing  and  the  larva  was 
extracted  after  about  six  weeks.  It  gave  rise  to  excruciating  pain  at 
intervals,  owing,  as  he  inferred  even  before  the  determination  of  the 
cause,  to  *  something  alive  beneath  the  skin.'  It  w^as  at  first  '  a  con- 
siderable tumefaction  over  the  tibia,  which  had  the  appearance  of  an 
ordinary  boil  (phlegmon)  ;  in  the  center  there  was  a  small  black  speck.' 

1  Ward,  H.  B.,  1903.  On  the  Development  of  Dermatobia  hominis.  Mark 
Anniversary  Volume,  Article  XXV,  pp.  483-512.  (Includes  a  discussion  of 
synonymy  of  species). 


MYIASIS 


259 


The  tumor  began  to  discharge  at  about  four  weeks,  and  was  so  serious 
that  he  was  '  scarcely  able  to  walk.'  Scarifying  the  tumor  yielded  no 
results,  and  finally  poulticing  with  cigar  ashes  and  rum  for  five  days 
resulted  in  the  extraction  of  the  larva  dead.  Dr.  Brick  records  that  '  it 
had  traveled  on  the  periosteum  along  the  tibia  for  at  least  two  inches.' 
While  other  authors  hold  very  generally  that  the  larva  always  inhabits 
a  fixed  spot  in  the  subcutaneous  tissues,  I  do  not  find  that  any  one 
has  referred  to  this  record  of  migration  made  by  a  most  competent 
observer." 

The  following  observation  made  by  Miller  (Journ.  Amer.  Med.  Assoc, 
Vol.  LV,  pp.  1978-1979)  throws  more  light  on  the  matter  of  migration, 
although  in  this  case  the  grub  was  Hypoderma  lineata.  "  In  December, 
1907,  the  boy  noticed  a  small  round  lump  just  below  the  left  knee ;  this 
lump  was  slightly  red  and  very  tender,  especially  at  night.  About  two 
days  later  the  lump  had  disappeared  from  its  original  position  and  was 
found  some  three  inches  above  the  knee ;  the  following  day  it  was  still 
higher  in  the  thigh,  and  during  successive  days  it  appeared  at  different 
points  along  a  course  up  the  abdomen,  under  the  axilla,  over  the  scapula, 
up  the  right  side  of  the  neck,  irregularly  about  the  scalp,  finally  passing 
back  of  the  ear  and  to  the  submental  region,  which  it  reached  about  two 
months  after  its  first  appearance ;  there  it  remained  stationary.  The 
extracted  larva  was  identified  by  Doctor  Stiles  as  Hypoderma  lineata." 

Identification  of  Myiasis-producing  Larvae.  —  The  value  of  a  simple 
method  for  the  identification  and  classification  of  dipterous  larvae 
involved  in  myiasis  is  no 
doubt  evident  to  the  student 
of  this  subject.  Instances  are 
few  in  which  the  larvae  can  be 
reared  to  the  adult  condition, 
when  identification  could  of 
course  be  readily  made. 
Authorities  are  now  for  the 
most  part  agreed  that  the 
posterior  spiracles  afford  the 
most  useful  diagnostic  char- 
acters, since  these,  wdiile  dif- 
fering consistently  in  position, 
form  and  structure  for  the 
genera  and  species,  show  little 
or  no  variation  within  the 
species  except  in  a  few  species 
in   the   very   early   stage   immediately   after   hatching. 

To  prepare  the  specimen  for  study  it  is  necessary  to  first  remove  by 
means  of  a  sharp  razor  the  extreme  posterior  end  (usually  the  broader), 
—  a  very  thin  section  is  needed.  This  section  is  then  boiled  until  quite 
clear  in  a  2  per  cent  solution  of  potassium  hydroxide  (KOH),  or  by 


Fig.  168.  — ■  Posterior  view  (.sligmal  held)  of  the 
larva  of  Calliphora  tomitoria,  showing  stigmal 
plates.  (1)  ring;  (2)  button;  (3)  slit-like 
spiracles. 


260       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

soaking  in  xylol  for  a  few  hours,  after  which  it  is  prepared  in  the 
usual  way  for  microscopic  study. 

It  will  be  seen  (Fig.  168)  that  there  are  two  stigmal  plates  more  or 
less  separated  from  each  other,  within  which  are  situated  the  spiracles, 
one  to  three  in  number,  either  slit-like,  sinuous  or  more  or  less  circular. 
There  may  or  may  not  be  present  a  "  button,"  i.e.  a  prominence  located 
at  the  narrower  segment  of  the  ring  or  periphery  of  the  stigmal  plate ; 
the  "  button  "  may  or  may  not  be  present  in  the  species  possessing 
slit-like  spiracles. 

In  using  the  posterior  spiracles  as  diagnostic  characters,  the  above 
conditions  are  considered,  i.e.  (1)  diameter  of  the  stigmal  plate,  the  space 
occupied  by  one  stigmal  plate  on  a  line  drawn  through  the  center  of  both  ; 
(2)  length,  when  slits  are  absent,  the  space  occupied  by  a  plate  on  a  line 
drawn  dorsoventrally  through  the  center  of  the  plate ;  or,  when  slits 
are  present,  the  space  occupied  by  a  plate  along  a  line  drawn  from  the 
lower  edge  of  button  (or  space  if  button  is  absent)  through  the  longest 
slit  (middle  slit)  to  the  margin  of  the  plate  ;  (3)  width,  along  a  line  drawn 
at  the  middle  of  the  plate  at  right  angles  to  the  length  line  ;  (4)  distance 
between  the  plates  ;  (5)  general  form  of  the  plates  ;  (6)  shape  of  spir- 
acles ;  (7)  presence  or  absence  of  hution ;   (8)  general  structure  of  plate. 

The  following  key,^  W'hile  still  somewhat  unsatisfactory,  serves  to 
classify  the  principal  families  of  Diptera  which  include  genera  and 
species  relating  to  myiasis.  In  this  key  the  entire  larva  is  needed  for 
identification. 

KEY  TO  THE  IDENTIFICATION  OF  LARVAE  OF  THE  DIPTE- 
ROUS FAMILIES  AND  CERTAIN  SUBGROUPS  WHICH  IN- 
CLUDE  GENERA  AND  SPECIES  RELATING   TO   MYIASIS 

I.    (a)  Body  cylindrical,  tapering  anteriorly II 

(6)  Body  robust,  ovate,  cylindrical,  rounded 

at  the  ends,  slightly  depressed (Estridce 

e.g.  Gastrophilus  equi,  (Estrus 
ovis,  Hypoderma   lineata 

(c)  Body  elliptical,  much  depressed  dorso- 

ventrally;     segments    provided 

with  long  spiny  processes Homalomyia 

(sub-group  of  Anthomyidse) 
e.g.  Fannia       {Homalomyia) 
canicxdaris,  Fannia  (Ho- 
malomyia) scalaris 

(d)  Body  with  long  tail-like  process Eristalis 

e.g.  Eristalis  tenax 
II.    (a)  With  one  anterior  booklet ;  stigmal  field 
slightly    depressed;     area    sur- 
rounding stigmal  field  usually  de- 
void of  tubercles,  which  if  present 

1  The  author  is  indebted  to  Mr.  I.  M.  Isaacs  for  much  careful  and  tedious 
work  in  the  construction  of  the  above  key. 


MYIASIS 


261 


are  small  and  insignificant; 
spinose  areas  onlj^  on  ventral  sur- 
faces of  segments 

(6)  With  two  anterior  booklets     .... 
III.    (a)  Posterior  spiracles  with  sinuous  slits  .     . 


(b)  Posterior  spiracles  with  three  short 
straight  slits  in  each  plate;  few 
faint  tubercles  around  stigmal 
field 


.     .     Ill 
.     .     IV 

Muscina 


Muscidce    (except 

subgroup) 
e.g.   Musca  domestica,    Sto 

moxys  calcitrans,  Hcema 

tohia  serrata 


IV.  (a)  Spinose  areas  completely  surrounding 
segment  and  occasionally  supple- 
mentary^ pads  on  the  lateral  sur- 
faces       

(1)  Stigmal  field  depressed  and  sur- 
rounded by  prominent  tubercles ; 
posterior  spiracles  with  three  dis- 
tinct slits  in  each  plate ;  plates 
directed  more  or  less  toward  each 
other    


e.g. 


.     .     Muscina  subgroup 
Muscina  stabulans 


(1)  or  (2) 


e.g 


(2)  Very  small  (not  over  4^5  mm.) ;  an- 
terior spiracles  with  few,  but  com- 
paratively long  lobes;  posterior 
spiracles  on  end  of  two  cylindrical 
processes  extending  posteriorly 
from  the  dorsal  part  of  the  tips  of 
the  body 


.  .  .  .  Sarcophagidce 
,  Calliphora  vomitoria, 
Calliphora  erythrocephala, 
Lucilia  coesar,  Lucilia 
sericata,  Chrysomyia 

macellaria,  Auchmero- 
myia  luteola 


(6)  Spinose  areas  on  ventral  and  lateral  sur- 
faces ;  stigmal  field  slightly  de- 
pressed and  surrounded  by  short 
fleshy  tubercles 


(c)  Body  segments  with  spinose  areas  only 
on  ventral  surfaces ;  anterior  spir- 
acles with  a  large  number  (20  ± ) 
of  lobes ;  sHghtly  depressed  or  flat 
stigmal  field ;  no  tubercles ;  pos- 
terior spiracles  with  three  short 
almost  parallel  slits,  those  of  one 
plate  pointing  toward  those  of  the 
other ;  plates  lacking  brown  chi- 
tinous  borders;  anal  tubercles 
prominent,  rounded  and  flattened  . 


DrosophilidcE 

e.g.  Drosophila  ampelophila 


Anfhomyidoe  (except  Homalo- 

myia  subgroup) 
e.g.  Anthomyia  radicum,  Phor- 
hia  hrassicce 


TrypetidcB 

e.g.  Ceratitis  capitata,  Dacus 
oleoB 


262       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

The  following  species  may  be  more  or  less  easily  identified : 

Family  Muscidce 

Musca  domestica,  Linn.  Stigmal  field  usually  slightly  concave  and  the 
surrounding  area  devoid  of  distinct  tubercles  ;  stigmal  plates  prominent, 
somewhat  longer  than  wide,  D-shaped,  flat  sides  facing,  about  one  third 
diameter  apart;  spiracles  apparently  three  in  number  and  sinuous; 
button  absent  in  first  stage  on  hatching ;  button  present  thereafter, 
large  and  very  dark,  embedded  near  the  center  of  the  flattened  side  of 
stigmal  plate  ;   ring  heavy  and  dark.     (Larva  of  house  fly.) 

Stomoxys  calcitrans,  Linn.  The  stigmal  field  is  slightly  convex  and 
is  in  the  dorsal  half  of  the  posterior  end.  There  are  no  tubercles  out- 
lining the  field.  The  species  can  easily  be  recognized  not  only  by  the  size 
and  shape  of  the  spiracles  but  by  the  distance  between  the  two  plates, 
there  being  from  two  and  a  half  to  three  diameters  between  them.  The 
plates  themselves  are  small,  triangular  in  shape  and  black  in  color.  In 
this  species  each  of  the  slits  is  surrounded  by  light  areas  which  appear  in 
each  corner  of  the  triangular. plates.     (Larva  of  biting  stable  fly.) 

HcBniatobia  serrata  R.  Desv.  The  stigmal  field  of  //.  serrata  is 
neither  depressed  nor  outlined  by  tubercles.  In  shape  the  stigmal 
plates  are  D-shaped,  as  are  those  of  M.  domestica,  but  are  proportion- 
ately much  narrower.  They  are  very  dark  in  appearance,  due  to  the  fact 
that  the  black  chitinous  edges  are  joined  to  the  comparatively  large 
black  button,  by  three  wide  chitinous  stripes.  Portions  of  the  sinuous 
slits  may  be  seen  in  the  small  clear  spaces  left  between  the  stripes. 
The  three-part  division  of  the  surface  is  very  similar  to  that  found  in 
the  spiracles  of  Stomoxys  calcitrans.  The  plates  are  about  one  fourth 
of  their  diameters  apart  and  therefore  close  together  compared  to  Musca 
domestica.  In  some  cases  there  is  a  tendency  toward  a  slightly  triangular 
shape  in  the  spiracles.     (Larva  of  horn  fly.) 

Muscina  stahulans  Fallen.  The  stigmal  field  is  not  depressed  and 
faint  tubercles  may  be  seen  dorsal  to  it.  The  spiracles  are  fairly  promi- 
nent, almost  round  in  shape  with  the  inner  border  slightly  flattened, 
black,  with  three  short  slits  in  each  plate  pointing  toward  those  of  the 
opposite  plate,  and  from  one  third  to  one  half  a  diameter  apart.  (Larva 
of  non-biting  stable  fly.) 

Family  Sarcophagidce 

Calliphora  erythrocephala  Mg.  The  stigmal  field  is  slightly  de- 
pressed. The  stigmal  plates  are  small  and  about  one  diameter  apart. 
The  slits  in  each  plate  converge  more  than  do  those  of  the  other  species 
mentioned  and  point  almost  directly  toward  those  of  the  opposite  plate. 
In  the  first  period  the  plates  are  about  as  long  as  they  are  wide,  occasion- 
ally being  slightly  wider,  there  being  no  button.     In  the  second  period 


MYIASIS  263 

they  are  slightly  longer  than  they  are  wide,  there  being  a  prominent, 
bullet-shaped  button,  and  the  ring  is  dark  and  very  heavy.  (Blue- 
bottle fly  larva.) 

Lucilia  coesar  Linn.  The  stigmal  field  is  slightly  depressed  and  is 
outlined  by  somewhat  fleshy  tubercles.  The  stigmal  plates  themselves 
are  longer  than  they  are  wide  and  are  considerably  larger  than  are  those 
of  C.  erythrocephala.  A  well-developed  button  is  present.  The  ring 
is  thin  and  delicate.  The  slits,  although  directed  more  or  less  toward 
those  of  the  opposite  plate,  point  more  toward  the  ventral  surface  than 
do  those  of  C.  erythrocephala  and  do  not  converge  as  much.  (Larva  of 
the  greenbottle  fly.) 

L2mlia  sericata  Mg.  The  stigmal  field  is  well  depressed  and  is 
outlined  by  tubercles  more  or  less  conical  but  not  very  sharp.  The  stig- 
mal plates  are  comparatively  large  in  both  the  first  and  second  period. 

In  the  first  period  the  plates  are  wider  than  they  are  long  and  are 
close  together,  being  only  about  one  eighth  of  a  diameter  apart.  The 
slits  are  long  and  rather  narrow,  pointing  ventrally,  those  of  one  plate 
being  directed  in  some  measure  toward  those  of  the  opposite  plate. 
There  is  no  button. 

In  the  second  period  the  plates  are  proportionately  longer  than  in  the 
first  period  and  they  are  about  one  fourth  of  a  diameter  apart.  The  slits 
also  are  wider  in  proportion  and  although  still  directed  ventrally  they 
point  slightly  more  toward  those  of  the  opposite  plate.  Care  must  be 
taken  as  to  the  exact  meaning  of  length  and  width  in  this  species. 
(Larva  of  sheep  maggot  fly.) 

Chrysomyia  macellaria  Fabr.  The  stigmal  field  is  a  very  deep 
depression  of  the  dorsal  half  of  the  posterior  end.  The  depression  is  so 
deep  that  the  lip-like  edges  of  the  last  segment  almost  conceal  the 
spiracles.  Outlining  the  stigmal  field  are  small  but  sharp  tubercles. 
The  stigmal  plates  are  fairly  large  and  are  about  as  long  as  they  are 
wide.  There  is  no  button.  In  the  first  period  the  plates  are  about 
one  fourth  of  a  diameter  apart,  while  in  the  second  period  they  are  a 
little  over  one  half  of  a  diameter  apart.  The  slits  point  ventrally, 
those  of  one  plate  being  directed  in  some  measure  toward  those  of 
the  onnnsite  plate.     (Larva  of  Texas  screw  worm  fly/ 

Family  AnthomyidcB 

Fannia  (Homalomyia)  canicularis  Linn.  Each  segment  is  provided 
with  long,  bristly,  sharp,  spiny  processes.  The  posterior  spiracles  are 
situated  on  the  anterior  part  of  the  last  segment,  they  are  raised,  three- 
lobed  processes.  The  lobes  are  distinct  and  can  easily  be  seen.  The 
larvae  are  about  8  mm.  in  length  when  fully  grown.  (Larva  of  the  lesser 
house  fly.) 

Fannia  (Homalomyia)  scalaris  Fabr.  The  processes  on  each  seg- 
ment are  feathery  rather  than  sharp  or  spiny  and  are  not  quite  as  long  as 


264       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

the  processes  of  F.  canicularis.  The  posterior  spiracles  also  differ  in  the 
two  species,  the  lobes  not  being  as  well  marked  in  F.  scalaris.  The 
larvse  are  from  7  to  8  mm.  in  length  when  fully  grown.  The  feathery- 
appearance  of  the  processes  on  the  segments  as  compared  to  the 
spiny  condition  in  F.  canicularis  is,  however,  most  useful  in  distinguish- 
ing the  two  species.     (Larva  of  the  latrine  fly.) 

Family  Trypetidw 

Ceratitis  capitata  Wied.  The  stigmal  field  as  a  whole  is  not  de- 
pressed nor  is  it  outlined  by  tubercles,  but  occasionally  each  stigmal 
plate  appears  to  be  situated  in  a  slight  depression  of  its  own.  The 
plates  are  fairly  prominent  and  are  about  twice  as  wide  as  they  are  long. 
In  accordance  with  the  group  character,  there  is  no  visible  chitinous 
edging  outlining  the  plates.  The  slits  of  each  spiracle  are  almost  parallel 
and  point  directly  toward  those  of  the  opposite  plate.  The  spiracles 
differ  from  those  of  D.  oleoB  only  in  the  distance  separating  the  two 
plates,  they  being  about  one  diameter  apart.  (Larva  of  Mediterranean 
fruit  fly.) 

Dacus  olecB  Meig.  The  appearance  of  the  stigmal  field  and  pos- 
terior spiracles  of  this  species  are  very  much  like  those  of  the  previous 
species,  except  for  the  fact  that  the  plates  are  from  one  and  a  half  to  two 
diameters  apart.  As  in  C.  capitata  there  is  no  chitinous  border  out- 
lining the  spiracles,  which  are  about  twice  as  long  as  they  are  wide. 
The  short  straight  slits  of  one  plate  point  almost  directly  toward  those 
of  the  opposite  plate.     (Larva  of  olive  fly.) 

Family  (Estridce 

Gastrophilus  equi  Fabr.  One  of  the  smallest  of  the  CEstridse.  A 
full-sized  larva  is  about  17  mm.  in  length  and  8  mm.  in  width  at  its  widest 
part.  It  is  compressed,  in  some  measure,  dorsoventrally.  It  is  wide 
and  thick  near  the  posterior  end  and  tapers  almost  to  a  point  anteriorly. 
The  spines  surrounding  each  segment  are  large  and  sharp.  The  two 
anterior  hooks  are  prominent. 

The  stigmal  field  of  this  species  is  drawn  well  into  the  anterior  por- 
tion of  the  last  segment  and  is  completely  covered  and  protected  by  a 
prolongation  of  the  outer  edges  of  this  segment. 

On  a  hard,  chitinous  background  are  six  long,  large,  bent  slits,  bilater- 
ally placed,  three  on  either  side  of  a  small  diamond-shaped  hollow. 
(The  larva  of  the  horse  botfly.) 

Hypoderma  lineata  De  G.  is  a  large  and  fleshy  grub  and  when  fully 
developed  is  about  25  mm.  in  length  and  11  mm.  in  width  at  its  widest 
part.  It  is  considerably  depressed  dorsoventrally  and  the  segments 
are  spinose  although  the  large  separate  spines  found  in  Gastrophilus  equi 
are  not  present. 


MYIASIS  265 

The  stigmal  field  is  depressed  but  is  not  covered  by  any  prolongation 
of  the  edges  of  the  last  segment.  The  spiracles  are  large,  close  together 
and  grossly  granular  in  appearance,  in  some  cases  being  more  or  less 
furrowed.  A  good-sized  button  is  embedded  near  the  inner  border  of 
each  plate  and  in  many  cases  a  clear  ungranulated  stripe  is  found  on  the 
chitinous  background  between  the  button  and  the  inner  border.  The 
plates  usually  appear  to  be  dark  brown  with  the  button  a  little  lighter  in 
color.     (The  ox  warble.) 

CEstrus  ovis  Linn.,  when  fully  developed,  is  about  28  mm.  in  length 
and  8-10  mm.  in  width.  It  is,  therefore,  longer  and  narrower  than  H. 
lineata,  a  condition  which  gives  it  a  more  rounded  appearance.  The 
dorsoventral  compression,  however,  is  noticeable.  The  segments  are 
spinose. 

The  stigmal  field  is  depressed.  The  plates  are  roughly  round,  with 
the  inner  borders  flattened.  The  plates  are  very  dark,  finely  granular 
in  appearance  with  a  somewhat  indistinct  button  in  the  center  of  each 
plate.     (The  sheep  head  maggot.) 


CHAPTER   XVII 


FLEAS  AND  LOUSE  FLIES 


A.   Fleas 


Order  Siphonaptera 

Structural  Characteristics.  —  Fleas  are  laterally  compressed,  wing- 
less, highly  chitinous,  mostly  leaping  insects  of  small  size,  inhabiting  by 
preference  certain  warm-blooded  hosts  and  are  blood-sucking  in  both 
sexes.  In  size  the  common  fleas  vary  from  1.5  to  4  mm.  in  length, 
according  to  the  species,  though  there  is  comparatively  little  variation 
within  a  given  species.  The  males  are  as  a  rule  somewhat,  often  con- 
siderably, smaller  than  the  females.  Nearly  all  fleas  have  the  ability 
to  leap,  though  the  Chigoe  fleas,  especially  the  females,  are  more  or  less 
sessile. 

The  posterior  edges  of  the  abdominal  segments  are  provided  with 
backward-extending  spines,  which  hinder  backward  motion  through  the 

hair  of  the  host.  The  piercing  mouth 
parts  (Figs.  169-170)  of  the  adult  fleas 
are  flattened,  blade-like  structures  con- 
sisting of  a  pair  of  triangular  maxillae 
with  jointed  palpi  between  which  are 
located  the  organs  of  the  proboscis 
proper,  i.e.  an  outer  pair  of  structures 
comprising  the  labium  which  ensheaths 
loosely  the  inner,  more  slender  stylets, 
—  a  pair  of  mandibles  with  serrate 
edges,  and  a  smooth  labrum  (hypo- 
pharynx?).  On  the  small  head  are 
also  located  the  sunken  antennae  wdth 
annulated  knobs,  and  the  inconspicuous 
simple  eyes  (absent  in  some  species). 
In  some  species  of  fleas  the  head  is 
provided  with  rows  of  spines  (Fig.  171), 
the  ctenidia,  a  valuable  characteristic  in  classification ;  the  ctenidia 
may  be  located  just  above  the  mouth  parts  and  are  then  said  to  be 
oral,  or  may  be  situated  back  of  the  head  and  are  then  thoracic  or 
pronotal  (both  sets  may  be  present) . 

The  legs  consist  of  five  joints ;    viz.  the  coxa  (the  joint  nearest  the 

266 


Fig.  169.  —  Photomicrograph  of  the 
mouth  parts  of  a^  flea,  —  front  view. 
(For  identificatiou  of  parts  see  next 
figure.) 


FLEAS  AND   LOUSE   FLIES 


267 


body),  the  trochanter,  a  very  small  segment  between  the  coxa  and  the 
femur,  the  tibia  (strongly  spined),  and  the  five-jointed  tarsus  terminating 
in  a  pair  of  ungues  or  claws  (Fig.  171). 

Life  History.  —  The  eggs  of  the  flea  (Fig.  172a)  are  large  (.5  mm. 
long),  glistening  white,  blunt  at  both  ends.  Comparatively  few  eggs 
are  deposited,  the  observed  range  being  from  3  to  18.     Most  species 


mwUUrH 


m^;(UU 


m^xilU 


maxUlicu 


maxiUi 


Fig.   170.  —  Showing  mouth  parts  of  a  flea.     A,  front  view;   B,  side  view. 

deposit  dry  eggs  and  hence  they  do  not  become  attached  to  the  hairs 
of  the  host  even  though  oviposition  has  taken  place  there.  There  is 
every  reason  to  believe  that  some  species  of  fleas  seldom  or  never  de- 
posit their  eggs  among  the  hairs  of  the  host,  preferring  the  loose  earth, 
excrement,  dust,  etc.  Captured  fleas  will  readily  oviposit  in  glass  vials 
or  other  receptacles.  If  deposited  on  a  dog,  for  example,  the  dry  eggs 
fall  off  readily  when  the  animal  stretches  and  shakes  itself  ;  thus  myriads 
of  eggs  may  be  found  on  the  sleeping  mat  of  a  flea-infested  animal. 

The  length  of  time  required  for  the  egg  stage  depends  largely  if  not 
wholly  on  temperature.  High  mean  temperature  from  35°  C.  to  37°  C. 
inhibits  development,  which  may  account  for  the  fact  that  the  eggs  do  not 
hatch  well  on  the  host.  At  a  temperature  of  from  17°  C.  to  23°  C.  Mitz- 
main  ^  found  that  the  egg  stage  lasted  from  seven  to  nine  days ;  at  from 


1  Mitzmain,  M.  B.,  1910.     General   observations   on  the  bionomics  of  the 
rodent  and  human  fleas.     U.  S.  Public  Health  Service  Bull.  38. 


268       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


J3 


FLEAS  AND   LOUSE   FLIES 


11°  C.  to  15°  C.  it  lasted  about  fourteen  days.     Atlantic  Coast  observers 
have  found  that  this  stage  may  be  passed  in  from  two  to  four  days. 

The  embryo  is  provided  with  a  sharp  spine  on  the  head  by  means  of 
which  the  egg  shell  is  cut  into  shreds  by  a  tumbling  motion  of  its  inhab- 
itant, which  is  thus  liberated.  The  larvae  (Fig.  1726)  are  very  active, 
slender,  13  segmented,  yellowish  white  maggots,  with  segmentally  ar- 
ranged bristles.  The  mouth  parts  are  of  the  biting  type  and  the  larvse 
subsist  on  organic  matter.  Very  little  food  seems  to  be  necessary  for 
their  development,  though  excrementous  matter,  e.g.  feces  from  rabbits, 
rats,  squirrels,  and  other  rodents,  also  dry  blood,  sprouting  grain,  etc., 
favor  growth.     Excessive  moisture  is  certainlv  detrimental  to  the  life 


Fig.   172.  —  Showing  life  history  of  a  rodent  flea,     a,  eggs;   6,  larva  ;   c,  pupa  in  cocoon ; 
d,  pupa  removed  from  cocoon;    e,  fleas,  —  male  (lower),  female  (upper).       X  12. 


of  the  larvae,  although  fewer  fleas  emerge  from  the  cocoon  during  periods 
of  hot  dry  weather.  The  larvae  are  usually  found  in  the  crevices  of  the 
floor  under  the  carpet  or  matting,  in  dusty  stables,  coops,  kennels,  nests 
of  rodents,  etc. 

The  length  of  the  larval  stage,  during  which  there  are  two  molts, 
is  also  influenced  by  temperature,  and  moisture  in  addition.  Under 
laboratory  conditions  with  room  temperature  this  stage  requires  from 
twenty-eight  to  thirty  days  and  over,  though  here  again  other  workers 
report  from  seven  to  ten  days.  At  the  end  of  the  larval  period,  the 
insect  spins  a  silken,  whitish  cocoon  (Fig.  172c)  in  which  transforma- 
tion takes  place.     The  pupa  (Fig.  \12d)  lies  within  this  cocoon. 

Warm,  moist  weather  favors  the  metamorphosis  of  the  pupa,  from 
which  the  fully  developed  imago  emerges  in  from  ten  to  fourteen 
days. 

Mitzmain  {loc.  cit.)  observed  one  individual  of  the  squirrel  flea 
(Ceratophyllns  acutus  Bak.)  from  egg  to  imago  with  the  following  results  : 
egg  stage,  eight  days ;  first  larval  stage,  six  days  ;  second  larval  stage,  ten 
days  ;  third  larval  stage,  twelve  days ;  cocoon  (pupal  stage),  twenty-one 
days;   total,  sixty-seven  days. 

The  following  table  (Table  XIII),  after  the  same  author,  indicates 


270       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

the  wide  variation  in  length  of  life  history  as  reported  by  various 
authorities. 

TABLE  XIII 

Time  Required  for  the  Life  Cycle  of  Fleas  in  Different  Countries 
Compiled  from  Accounts  of  Various  Authors  (Mitzmain) 


COUNTBY   AND   SPECIES 

OF  Flea 

Ego 

Larva 

Pupa 

Complete 
Generation 

India : 

L.  cheopis 

2  days 

1  week 

7  to  14  days 

21  to  22  days 

Australia : 

P.  irritans 

6  days 

12  days 

14  days 

4  to    6  weeks 

Europe : 

P.  irritans 

4  to  6  days 

11  days 

12  days 

4  to    6  weeks 

Ct.  canis 

2  weeks 

12  days 

10  to  16  days 

5  to    6  weeks 

United  States: 

Atlantic  Coast : 

P.  irritans  ] 
Ct.  canis     ; 

2  to    4  days 

8  to  24  days 

5  to    7  days 

2  to    4  weeks 

Pacific  Coast : 

P.  irritans    .... 

7  to    9  days 

28  to  32  days 

30  to  34  days 

9  to  10  weeks 

L.  cheopis    .... 

9  to  13  days 

32  to  34  days 

25  to  30  days 

9  to  11  weeks 

C.  acutus     .... 

7  to    8  days 

26  to  28  days 

24  to  27  days 

8  to    9  weeks 

C.  fasciatus      .     .     . 

5  to    6  days 

24  to  27  days 

24  to  26  days 

7  to    8  weeks 

Longevity  of  Fleas.  —  It  is  of  great  importance  to  know  how  long  a 
flea  will  live  with  and  without  food  under  various  conditions.  If  not 
provided  with  a  moist  medium  in  which  to  live  and  at  the  same  time  de- 
prived of  the  opportunity  of  feeding  on  a  warm-blooded  animal  the 
majority  of  fleas  die  in  about  six  days  or  less.  In  a  moist  medium  such 
as  wheat  grains  and  sawdust  (moistened),  Mitzmain  has  kept  squirrel 
fleas  alive  from  thirty-eight  days  in  one  case  to  sixty-five  days  in 
another,  the  former  a  male,  the  latter  a  female.  Rat  fleas  on  human 
blood  alone  averaged  eight  and  one  half  days  (maximum  seventeen)  for 
the  males,  and  thirty-two  and  four  fifths  days  (maximum  one  hundred 
and  sixty)  for  the  females. 

Hosts  and  Occurrence  of  Species.  —  As  will  be  seen  later  in  this 
chapter,  the  rodent  fleas  are  most  important  from  the  public  health  stand- 
point, and  transference  from  host  to  host  of  different  species  is  a  well- 
known  habit,  adding  much  to  the  danger  of  disease  transmission. 

It  is  true  that  ordinarily  a  certain  species  of  flea  is  found  to  predomi- 
nate on  a  given  species  of  host,  for  example  Ctenocephalus  canis  Curt, 
on  the  dog,  CeratophyUus  fasciatus  Bosc.  on  the  rat  in  the  United  States, 
Xenoysylla  cheopis  Roth,  on  the  rat  in  India,  CtenopsijUa  musculi  Duges 
on  the  mouse,  Pulex  irritans  Linn,  on  the  human,  etc. 

For  example,  in  an  unpublished  report  to  the  writer  on  the  species  of 
fleas  found  on  rats  in  San  Francisco,  Rucker  states  that  a  great  prepon- 
derance of  the  rat  fleas  recovered  in  San  Francisco  are  CeratophyUus 
fasciatus  as  based  on  10,972  specimens  as  follows : 


FLEAS  AND   LOUSE   FLIES 


271 


Ceratophyllus  fasciatus 68.07  % 

Xenopsylla  {Lamopsylla)  cheopis .21.36% 

Pulex  irritans        5.57  % 

Ctenopsylla  musculi 4.48  % 

Ctenocephalus  cams 52  % 

The  following  tables  (Tables  XIV-XX)  adapted  after  McCoy  ^ 
throw  much  light  on  the  interchange  of  hosts  and  predominance  of 
species : 

TABLE  XIV 
From  Brown  Rats  {Mus  norvegicus) 


No.  OF  Rats 

C.    FASCIATUS 

L.  CHEOPIS 

p.  IRRITANS 

Ct.  musculi 

Ct.  canis 

Combed 

Male 

Female 

Male 

Female 

Male 

Female 

Male 

Female 

Male 

Female 

606 

570 

1252 

790 

1146 

225 

425 

44 

137 

13 

15 

TABLE  XV 
From  Black  Rats  {Mus  rattus) 


No.  OP  Rats 

C.  fasciatus 

L.    CHEOPIS 

p.    IRRITANS 

Ct.  MUSCULI 

Ct,  canis 

Combed 

Male 

Female 

Male 

Female 

Male 

Female 

Male 

Female 

Male 

Female 

11 

7 

32 

6 

5 

0 

0 

4 

17 

0 

2 

TABLE  XVI 

From  Mice  {Mus  musculus) 

From  an  unknown  number  of  Mus  musculus 


C.  fasciatus 

L.  cheopis 

p.    IRRITANS 

Ct.  musculi 

Ct.  canis 

Male 

Female 

Male 

Female 

Male 

Female 

Male 

Female 

Male 

Female 

1 

5 

2 

0 

0 

0 

3 

10 

0 

0 

1  McCoy,  George  W.,   1909.     Siphonaptera  observed  in  the   Plague  Cam- 
paign in  California,  etc.     U.  S.  Public  Health  Reports,  Vol.  24,  No.  29. 


272       MEDICAL  AND   VETERINARY  J  ENTOMOLOGY 

TABLE  XVII 

Fbom  California  Ground  Squirrels  (Citellus  heecheyi) 


No.  OF  Squirrels 

C.    ACUTUS 

Hop.  anomaltjs 

Combed 

Male 

Female 

Male 

Female 

132 

2065 

2306 

86 

140 

TABLE  XVIII 

From  the  Dog  {Canis  jamiliaris) 


No. 

Ct. 

CANIS 

p.   IBRITANS 

Ct.  felis 

C.  ACtJTtrs 

Combed 

Male 

Female 

Male 

Female 

Male 

Female 

Male 

Female 

4 

10 

44 

8 

17 

0 

1 

1 

0 

TABLE  XIX 
From  the  Cat  {Felis  domestica) 


No.  Combed 

Ctenocephalus  felis 

Male 

Female 

2 

5 

15 

TABLE  XX 
From  Man  {Homo  sapiens) 


r  No.  of 
Individ- 
uals 

p.   IRBITANS 

Ct.  felis 

Ct.  CANIS 

C.   ACUTUS 

Male 

Female 

Male 

Female 

Male 

Female 

Male 

Female 

29 

117 

220 

1 

0 

1 

0 

1 

2 

FLEAS  AND  LOUSE   FLIES  273 

Light  Reactions.  —  In  a  series  of  light  reaction  experiments  by  the 
writer  on  two  species  of  fleas,  Pulex  irritans  and  Ceratophyllus  acutus,  it 
was  found  that  the  former  reacts  positively  and  directly  to  light  (incan- 
descent) at  10  CM.,  83+  CM.  and  100  CM.,  and  is  indifferent  to  7- 
CM.,  while  the  latter  species  reacts  negatively  to  higher  intensities, 
such  as  46+  CM.  and  83+  CM.,  and  is  indifferent  to  lower  intensities 
such  as  9+  CM.  and  7-  CM. 

The  larvae  of  C.  acutus  react  in  the  main  positively  to  light  in  their 
early  stages,  becoming  more  and  more  negative  as  they  grow  older. 
An  intensity  of  8.38  CM.  was  used  at  intervals  of  three  and  five  days. 

Chemical  Experiments.  —  To  determine  the  lethal  property  of  va- 
rious chemicals,  a  series  of  experiment  vials  were  made  after  the  fashion 
of  cyanide  bottles  for  killing  insects,  i.e.  a  chamber  was  prepared  into 
which  cotton  was  placed  soaked  in  the  material  to  be  tested  and  covered 
with  dry  blotting  paper,  the  fleas  thus  did  not  come  in  direct  contact  with 
the  chemical. 

It  was  found  that  certain  essential  oils,  such  as  lavender,  citronella, 
mirbane,  caraway,  peppermint,  eucalyptus  and  pennyroyal  have  a 
stupefying  effect  on  fleas  when  used  in  strong  concentrations,  50  per  cent 
and  over.  It  is  quite  probable  that  rubbing  the  body,  particularly  with 
oil  of  citronella,  would  act  as  a  fairly  good  repellent. 

Systematic.  —  Over  300  species  of  fleas  have  been  described,  of  which 
number  only  a  few  need  to  be  considered  here,  particularly  those  affecting 
rodents  and  man.  The  Siphonaptera  (also  referred  to  as  Aphaniptera) 
are  commonly  divided  into  three  families,  viz.,  Sarcopsyllidae,  Pulicidse 
and  Ctenopsyllidse.  The  following  keys  for  the  classification  of  fleas 
together  with  descriptions  are  adapted  mainly  after  Banks. ^ 

1 .  Thoracic  segments  much  shortened  and  constricted ;  labial  palpi  apparently 

not  jointed;  third  joint  of  antemiae  without  subjoints;  no  ctenidia; 
abdomen  of  female  becomes  more  or  less  swollen  .  .  Sarcopsyllidce 
Thoracic  segments  not  shortened  nor  constricted ;  labial  palpi  with  joints ; 
third  joint  of  antenna?  with  several  more  or  less  distinct  subjoints ;  ctenidia 
often  present ;  abdomen  of  female  never  distinctly  swollen  ....       2 

2.  Posterior  tibial  spines  in  pairs Pvlicidce 

Posterior  tibial  spines  mostly  single  and  more  numerous    .      Ctenopsyllidoe 

Family   PulicidcB 

1.  Head  without  ctenidia;    eyes  distinct       2 

Head  and  pronotum  with  ctenidia ;  last  tarsal  joint  with  four  pairs  of  lateral 

spines 5 

2.  Pronotum  without  ctenidia 4 

Pronotum  with  ctenidia         3 

3.  Female  with  one  antepygidial  bristle  on  each  side     .     .     .     Hoplopsyllus 
Last  tarsal  joint  with  five  pairs  of  lateral  spines;   female  with  two  to  five 

antepygidial  bristles  each  side Ceratophyllus 

1  Banks,  Nathan,  1910.  The  ectoparasites  of  the  rat.  A  symposium  on 
"The  Rat  and  its  Relation  to  the  Public  Health."  U.  S.  Pub.  Health  Service 
BuU.,  Washington,  D.C. 


274       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

4.  Mesosternite  very  narrow,  without  internal  rod-like  incrassation  from  the 

insection  of  coxa  upward Pulex 

Mesosternite  with  a  rod-like  internal  incrassation  from  insection  of  coxa 
upward Xenopsylla 

5.  Eyes   rudimentary;    female  with  two  to  five   antepygidial   bristles   each 

side Neopsylla 

Ej^es  distinct ;  female  with  one  antepygidial  bristle  each  side   Ctenocephalus 

Family   Sarcopsyllidoe 

"  The  fleas  of  this  famil}'  are  commonly  called  *  chigoes,'  '  jiggers  ' 
or  sand  fleas.  The  head  is  usually  larger  proportionately  than  in  other 
fleas  ;  there  are  no  ctenidia  on  head  or  pronotum  ;  the  thoracic  segments 
are  extremely  short,  and  in  the  female  the  abdomen  enlarges  with  the 
development  of  the  eggs.  They  do  not  hop  about  as  other  fleas,  but  re- 
main on  the  spot  to  which  they  have  attached  themselves,  until  they 
die.  Frequently  the  adjacent  skin  grows  over  them,  forming  a  swelling 
of  considerable  size." 

1.   Angle  of  head  acutely  produced ;  fifth  tarsal  joint  of  hind  legs  without  heavy 

spines ;  few  spines  on  the  legs Sarcopsylla 

■    Angle  of  head  not  produced,  obtuse;    fifth  tarsal  joint  with  heavy  lateral 
spines  and  other  spines  on  other  parts  of  the  legs     .     .     Echidnophaga 

Family   Ctenopsyllidce 

"To  this  family  belongs  the  Ctenopsylla  musculi  Duges  (Fig.  173). 

"  This  was  formerly  placed  in  the  genus  Typhlopsylla.  The  head  is 
rather  acute  in  front  and  has  four  ctenidia  each  side ;  the  eyes  are  very 
small ;   the  pronotal  comb  has  22  spines ;   each  dorsal  segment  of  the 


Fig.  173.  —  Ctenopsylla  musculi,  a  mouse  flea;   male,  right;   female,  left.     X  17. 

body  has  two  rows  of  hairs ;  the  basal  row  of  smaller  hairs.  The  pro- 
portions of  joints  in  the  hind  tarsus  are:  45-25-17-8-14.  Length  1.8 
to  2.5  mm.  This  species  is  abundant  on  rats  and  mice  in  Europe  and 
other  countries ;  recently  it  has  been  taken  in  California  and  Florida 
on  rats  and  mice." 


FLEAS   AND  LOUSE   FLIES 

The  Commoner  Species 


275 


Pulex  irritans  Linn,  (Fig.  174).  "The  mandibles  reach  about  half- 
way down  on  the  anterior  coxte ;  the  head  is  regularly  rounded  in 
front ;  two  bristles  on  the  gena,  one  placed  low  down  just  above  the 
maxilla,  the  other  below  the  eye ;  there  are  no  transverse  rows  of  bristles 


Fig.   174.  —  Pulex  irritans,  the  human  flea ;   male,  right ;   female,  left.      X  17. 

on  the  vertex,  and  but  one  row  of  bristles  on  each  abdominal  tergite. 
The  proportions  of  the  joints  of  the  hind  tarsus  are :  5-30-18-12-32. 
Color,  usually  yellow-brown.  Male,  1.6  to  2  mm. ;  female,  2  to  3.5 
mm. 

"  This,  the  human  flea,  is  quite  cosmopolitan,  but  more  abundant  in 
warm  countries  than  elsewhere.  It  occurs  on  many  domestic  animals 
and  has  frequently  been  taken  from  rats  in  California  and  elsewhere ; 
it  also  occurs  on  skunks." 

Ctenocephalus  canis  and  fells  (Fig.  175).  "The  common  fleas  on 
cats  and  dogs,  as  well  as  on  man,  belong  to  two  species  long  kept  under 


Fig.  175.  —  Ctenecephalus  cania,  the  cat  and  dog  flea;    male,  left;   female,  right.     X  17* 

one  name  (C  canis  or  C.  serraticeps) ,  but  lately  shown  by  Rothschild 
to  be  distinct.     Both  have  a  comb  of  eight  spines  on  the  head  and  sixteen 


276       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

spines  in  pronotal  comb  ;  the  proportions  of  joints  in  the  hind  tarsus  are : 
40-24-15-10-24.     They  may  be  separated  as  follows : 

1.  In  the  female  the  head  is  fuUy  twice  as  long  as  high  (seen  from  side) ;  the 
first  spine  of  genal  comb  is  two  thirds  the  length  of  the  second ;  in  male 
the  manubrium  of  claspers  is  barely  enlarged  at  tip ;   and  with  two  rows 

of  hairs  on  disk  of  movable  finger C.  felis  Bouch6 

In  the  female  the  head  is  less  than  twice  as  long  as  high  (seen  from  side)  ; 
the  first  genal  spine  in  the  head  comb  is  only  about  one  half  the  length 
of  the  second;  in  the  male  the  manubrium  of  clasper  is  very  distinctly 
enlarged  at  tip;  but  one  row  of  hairs  oil  the  disk  of  the  movable 
finger .     C.  canis  Curtis 

Ceratophyllus  fasciatus  Bosc.  (Fig.  176).  "  There  are  eighteen  or 
twenty  spines  in  the  pronotal  comb ;  there  are  three  bristles  in  front 
of  eye  and  in  female  two,  and  in  male  four  in  front  of  these ;   there  are 


Fig.   176.  —  Ceratophyllus  fasciatus,  the  rat  flea;    male,  left;    female,  right.      X  17. 

three  or  four  hairs  on  the  inner  surface  of  the  hind  femur ;  the  propor- 
tions of  joints  in  the  hind  tarsus  are :  50-33-20-1 1-21 .  The  manubrium 
of  the  male  claspers  is  very  long  and  slender,  and  some  of  the  bristles 
on  the  movable  finger  are  as  long  as  the  joint.  Length,  male,  1.8  mm. ; 
female,  2.5  mm. 

"  It  has  been  recorded  in  California  in  rats,  mice,  skunks  and  man. 
It  is  also  common  in  Europe  and  elsewhere  on  rats,  mice  and  other, 
small  animals." 

Ceratophylhis  acutus  Baker  (the  squirrel  flea)  (Fig.  177).  "  This 
species  is  readily  known  by  having  a  spine  at  tip  of  the  second  joint 
of  hind  tarsus  longer  than  the  third  joint  and  reaching  over  on  to  the 
fourth  joint;  the  abdominal  tergites  have  each  two  rows  of  bristles; 
the  male  claspers  are  very  large  and  long,  sickle  shaped.  Color,  pale 
brown.     Length,  3  to  3.5  mm." 

Ceratophyllus  niger  Fox.  "This  species  has  the  pronotal  ctenidia 
of  about  26  spines ;  there  are  a  few  hairs  on  the  inner  surface  of  hind 
femur;  apical  spines  of  second  joint  of  hind  tarsus  not  longer  than 
third  joint ;   three  hairs  in  front  of  the  eye  and  three  in  front  of  these ; 


FLEAS  AND  LOUSE  FLIES 


277 


movable  finger  of  claspers  with  five  slender  bristles  on  the  outer  edge. 

Color,  very  dark  brown.     Length,  3.5  mm. 

"Taken  in  California  from  Mus  decumanus  and  from  man." 
Ceratophylhis  londivetisis,  Rothsc.     "  This  species  is  closely  allied 

to  C.  fasciatus,  and  best  separated  from  it  by  the  shape  and  armature 

of  the  genital  parts ;   the  manubrium  is  not  as  long  as  in  that  species. 


Fig.   177.  —  Ceratophylhis  acutus,  the  squirrel  flea  ;   male,  right ;    female,  left.       X  17. 

and  the  bristles  on  the  movable  finger  are  shorter ;  the  third  joint  of 
the  maxillary  palpi  is  proportionately  longer  than  in  C.  fasciatus.  There 
are  three  bristles  in  front  of  the  eyes  and  four  or  five  in  front  of  these ; 
there  are  a  few  hairs  on  the  inner  surface  of  the  hind  femur ;  the  propor- 
tions of  the  joints  in  the  hind  tarsus  are :  46-30-18-11-18. 

"  It  has  been  recorded  by  Dr.  Fox  from  Mus  rattus  in  California, 
and  is  known  from  rats  and  mice  from  several  parts  of  Europe." 

Xenopsylla  cheopis  Rothsc.  (Fig.  178).  "The  mandibles  reach 
nearly  to  the  end  of  the  anterior  coxae ;    there  are  no  ctenidia  on  the 


Fig.  178.  —  Xenopsylla  cheopis,  the  oriental  rat  flea;   male,  left;   female,  right.      X  17. 

head  or  pronotum ;  two  bristles  on  gena ;  oral  bristles  placed  low  down 
just  above  the  base  of  the  maxilla ;  ocular  bristle  in  front  and  just  above 


278       MEDICAL  AND   VETERINARY   ENTOMOLOGY 

the  middle  of  the  eye;  the  eyes  are  distinct;  each  abdominal  tergite 
has  but  one  row  of  bristles ;  the  hind  femur  has  a  row  of  about  eight 
bristles ;  the  proportions  of  the  joints  in  the  hind  tarsus  are  as  follows  : 
40-30-16-10-20.  Color,  light  brown.  Male,  1.5  to  2.0  mm. ;  female, 
2  to  3.0  mm. 

"  This  is  a  true  rat  flea,  but  will  readily  bite  man,  and  is  the  species 
chiefly  concerned  in  transmitting  the  bubonic  plague.  It  is  widely 
distributed,  especially  in  seaport  towns." 

Hoplopsyllufi  anomalus  Baker.  "The  mandibles  scarcely  reach 
halfway  down  on  the  anterior  coxse ;  upon  each  are  two  large  spines ; 
the  pronotal  comb  has  about  nine  spines  each  side ;  and  each  abdominal 
segment  has  but  a  single  row  of  bristles.  The  hind  femora  have  six  to 
eight  bristles  on  the  side;  the  proportions  of  the  joints  in  the  hind 
tarsus  are:  26-16-8-5-13.  Color,  dark  reddish  brown.  Female,  2.5 
mm.;  male,  1.5  mm. 

"  Described  from  a  spermopile  from  Colorado  and  recorded  by  Dr. 
Fox  and  Professor  Doane  from  Mus  norvegicus  from  California." 

Echidnophaga  gallinacea  Westw.  "  This  species  has  the  body  almost 
as  broad  as  long,  and  of  a  red-brown  color;  one  bristle  in  front  of  eye 
and  six  on  each  metathoracic  pleuron;  each  abdominal  tergite  has 
on  each  side  near  the  median  line  a  single  hair ;  the  spiracles  are 
situated  well  down  on  the  sides.  Length:  male,  0.8  to  1.2  mm; 
female,  1  to  1.8  mm. 

"  This  species  is  a  fairly  common  pest  of  poultry  and  dogs  in  warm 
countries,  and  is  called  the  '  chicken  flea,'  or  *  stick  tight.'  " 

Sarcopsylla  penetrans  Linn.  This  species  differs  from  the  above 
in  that  the  eyes  and  antennae  are  situated  in  the  anterior  half  of  the 
head,  and  the  metathoracic  scales  are  rounded. 

Plague.  —  Plague  is  a  bacterial  disease  traceable  to  Bacillus  pestis, 
runs  a  raipid  course,  presents  a  high  mortality,  20  per  cent  to  95  per 
per  cent,  depending  upon  hygienic  and  social  conditions,  and  while  it  has 
appeared  in  devastating  epidemics  in  temperate  climates,  it  is  endemic 
in  certain  warmer  countries,  particularly  southern  India  and  China. 

Three  forms  of  the  disease  may  be  considered ;  namely,  huhonic, 
septiccsmic  and  pneumonic.  The  incubation  period  varies  from  two 
to  eight  days  ordinarily,  according  to  Manson,  though  longer  and 
shorter  periods  have  been  observed.  In  the  bubonic  plague,  which 
constitutes  by  far  the  greater  percentage  of  the  cases,  there  appear 
characteristic  swellings  (buboes)  in  the  groin  (femoral  glands),  axilla 
(axillary  glands)  or  other  parts.  These  buboes  vary  from  2  cm.  to 
10  cm.  in  diameter ;  these  appear  within  a  day  or  two.  In  septicsemic 
plague  the  bacilli  appear  in  the  blood  in  large  numbers,  there  is  a  com- 
parative absence  of  swellings,  the  disease  is  very  virulent  and  runs  a 
very  rapid  course,  terminating  in  death  in  from  one  to  three  days. 

In  pneumonic  plague  the  seat  of  the  disease  is  the  lungs.  This  form 
is  considered  most  fatal  and  most  infectious. 


FLEAS  AND   LOUSE   FLIES  279 

The  plague  bacillus  was  discovered  concomitantly  and  independently 
by  Kitasato  and  Yersin  in  1894,  when  it  became  established  that  rat 
plague  and  human  plague  are  identical.  Epidemics  of  plague  in  humans 
have  evidently  always  been  announced  by  fatal  epizootics  among  rats. 

Plague  Transmission.  —  Many  theories  have  been  advanced  to  ac- 
count for  the  transmission  of  plague,  notably  soil  and  climatic  conditions, 
but  apparently  insects  were  not  suspected  until  the  latter  part  of  the 
last  century.  Nuttall  ^  in  1897  demonstrated  the  presence  of  B.  pestis 
in  the  bodies  of  bedbugs  {Cimex  ledularius)  which  had  fed  on  the  bodies 
of  rats  sick  of  plague.  Simond  ^  in  1898  first  succeeded  in  transmitting 
plague  from  a  sick  rat  to  a  healthy  rat  through  the  agency  of  infected 
fleas.  Simond's  work  was  discredited  for  a  number  of  years,  but  was 
successfully  repeated  by  Verjbitski  ^  in  1903. 

Liston  ^  in  1904,  working  in  Bombay,  came  to  the  following  con- 
clusions :  (1)  There  was  one  flea  infecting  rats  in  India  far  more  commonly 
than  did  any  other,  viz.,  Xenopsylla  (Pulex)  cheopis  Rothsc. ;  (2)  that 
these  fleas  when  feeding  on  a  plague  rat  harbored  the  plague  bacillus 
in  their  bodies  and  that  it  multiplied  therein ;  (3)  that  where  fatal 
plague  occurred  many  of  these  infected  fleas  were  at  large,  and  (4)  that 
after  a  local  epizootic  of  rat  plague,  man  was  also  found  to  harbor  these 
rat  fleas  and  might  become  infected  as  had  the  guinea  pigs  used  in  the 
experiment. 

The  following  is  a  summary  of  experiments  conducted  by  the  Indian 
Plague  Commission  before  and  after  its  organization  in  1905. 

In  the  first  instance  healthy  rats  were  confined  in  close  proximity 
to  rats  which,  inoculated  with  plague,  had  succumbed  to  that  disease, 
and  that  previous  to  this  had  been  artificially  infected  with  rat  fleas 
{X.  cheopis).  The  separate  confinement  of  the  rats  in  each  case  was 
so  arranged  that  both  contact  with  and  access  to  all  excreta  were  ex- 
cluded, although  it  was  provided  that  the  fleas  could  pass  from  the 
inoculated  to  the  healthy  rats;  this  transfer  actually  did  take  place 
and  in  many  cases  these  fleas  contained  virulent  plague  bacilli ;  and 
when  healthy  non-immune  rats  were  thus  infected  they  died  of  plague 
to  the  extent  of  79  per  cent ;  this  extent  of  infection  fell  to  38  per  cent, 
when  partly  immune  rats  of  local  origin  were  employed. 

That  the  plague  had  originated  in  the  healthy  rats  through  the 
intermediary  of  the  rat  fleas  was  further  demonstrated  by  the  fact  that 
when  they  were  actually  transferred  from  artificially  plague-infected  to 
healthy  English  rats,  the  disease  resulted  to  the  extent  of  61  per  cent. 

Further,  on  constructing  a  series  of  miniature  houses  (godowns)  so 

iNuttaU,  G.  H.  F.,  1897  {loc.  cit.). 

2  Simond,  P.  —  L.  S.,  1898.  La  propagation  de  la  peste.  Ann.  de  I'lnst. 
Pasteur,  Vol.  XII,  p.  625. 

^Verjbitski,  D.  T.,  1908.  The  part  played  by  insects  in  the  epidemiology 
of  plague.     Journ.  of  Hyg.,  Vol.  VIII,  p.  162. 

*  Liston,  W.  G.,  1905.  Plague  rats  and  fleas.  Journ.  Bombay  Nat. 
Hist.  Soc,  Vol.  XVI,  pp.  253-273. 


280       MEDICAL  AND   VETERINARY   ENTOMOLOGY 

as  to  reproduce  the  conditions  pertaining  to  ordinary  domiciles,  it  was 
found  that  whenever  these  were  so  constructed  as  to  admit  rats  to 
their  roofs,  but  not  to  their  interiors,  guinea  pigs  confined  therein  be- 
came successively  infested  by  rat  fleas  and  infected  by  plague,  but  that 
in  those  houses  to  which  rats  could  not  gain  access  plague  was  originated 
in  guinea  pigs  living  therein,  either  by  transferring  rat  fleas  to  them, 
derived  from  plague-infected  guinea  pigs,  or  on  accidental  admission  of 
rat  fleas  from  other  sources.  Also,  that  when  so  confined,  guinea  pigs 
had,  under  these  conditions,  died  of  plague ;  healthy  flea-free  guinea 
pigs,  subsequently  introduced,  became  plague  smitten,  and  that  the 
contagion  remained  in  the  place  in  proportion  as  the  test  animals  were 
accessible  to,  and  were  found  to  be  infested  with,  fleas.  In  other  words, 
that  "  if  the  fleas  be  present,  the  rate  of  progress  being  in  direct  propor- 
tion to  the  number  of  fleas  present."  Further,  that  when  in  one  of 
the  houses,  to  the  interior  of  whose  roof  fleas  could  not  gain  access, 
healthy  guinea  pigs  were  confined,  guinea  pigs  became  flea  infested  and 
infected  when  running  on  the  ground,  to  a  less  extent  when  the  cage 
was  placed  two  inches  therefrom,  and  not  at  all  when  it  was  suspended 
two  feet  above  it.  The  fact  that  infection  took  place  where  rats  were 
located  two  inches  above  the  ground  indicates  that  contact  with  infected 
soil  is  not  necessary  for  plague  to  originate,  and  that  "  an  epizootic  of 
plague  might  start  without  direct  contact  of  healthy  with  infected 
animals." 

To  demonstrate  that  this  communication  of  plague  from  guinea 
pig  to  guinea  pig  was  through  the  intermediary  of  fleas,  rat  fleas  were 
taken  from  a  morbid  guinea  pig  and  allowed  to  feed  through  muslin  on 
healthy  animals.  The  positive  outcome  of  this  experiment  proved  the 
above  statement. 

The  state  of  affairs  that  existed  in  actual  domiciles  in  which  plague 
occurred  or  had  existed  was  next  inquired  into,  advantage  being  taken 
of  the  fact  that  plague-susceptible  guinea  pigs  would  serve  as  hosts  for, 
and  for  the  collection  of,  fleas. 

Guinea  pigs  free  from  fleas  were  introduced  into  rooms  in  which 
persons  had  died  of  plague,  or  from  which  plague-infested  rats  had  been 
taken.  They  were  allowed  to  be  at  large  in  these  rooms  for  periods  of 
from  eighteen  to  twenty-four  hours.  These  guinea  pigs  not  only  col- 
lected the  fleas  on  their  bodies,  most  of  which  were  rat  fleas,  but  29 
per  cent  of  them  contracted  plague  and  died  of  plague  within  a  few 
days  after  being  restored  to  ordinary  confinement.  As  before,  many 
of  the  fieas  which  they  yielded  harbored  plague  bacilli  in  their  stomachs, 
and  were  capable  of  infecting  additional  animals. 

Further,  after  first  washing  the  floors  and  walls  of  the  rooms  with 
an  acid  solution  of  perchloride  of  mercury,  and  so  adequately  disinfecting 
them  for  plague,  but  not  for  fleas,  and  then  introducing  guinea  pigs, 
these  latter  became  plague-infected  if  rat  fleas  were  present. 

That  the  infection  was  actually  due  to  fleas  was  also  shown  by  the 


FLEAS  AND   LOUSE   FLIES  281 

positive  results  from  fleas  collected  from  rats  occurring  in  plague- 
infected  houses  and  transferring  them  to  healthy  rats  or  guinea  pigs  in 
the  laboratory.     These  in  due  course  became  infected  and  died  of  plague. 

Similarly  fleas  taken  from  the  clean  guinea  pigs  allowed  to  run  in 
plague-infected  houses,  and  transferred  to  fresh  animals,  communicated 
plague  to  them  in  eight  out  of  forty  experiments. 

In  the  next  place,  plague-free  white  rats,  guinea  pigs  and  monkeys 
were  placed  in  enclosures,  which  precluded  contact  as  well  as  soil  in- 
fection, in  plague-infested  rooms,  pairs  of  one  animal  or  another  being 
used  in  each  of  the  forty-tw^o  experiments  of  this  class  conducted,  one 
individual  being  confined  to  a  flea-proof  receptacle  and  the  other  to  an 
adjacent  one  accessible  to  these  insects  (one  animal  being  thus  a  control). 
In  the  latter  case  plague  resulted  in  four  instances,  or  10  per  cent  gave 
positive  results. 

As  a  variation  of  the  same  experiments,  the  enclosures  for  individual 
animals,  whilst  protected  from  soil  or  contact  infection,  were  surrounded, 
as  a  screen  to  fleas,  by  2|  inches  of  "  tanglefoot  "  or  were  unprovided 
with  this  protection,  the  "  tanglefoot "  being  replaced  by  sand. 
(Twenty-nine  experiments  were  conducted.)  In  the  latter  case  the 
animal  became  infested  with  fleas,  one  having  as  many  as  twenty; 
seven  became  fatally  infected  with  plague.  In  the  former  individual 
fleas  were  only  found  on  three  of  the  rats  and  no  animals  became  plague- 
infected. 

Examining  the  fleas  entrapped,  247  in  number,  it  was  found  that 
147  were  human  fleas,  84  were  rat  fleas,  and  16  cat  fleas.  Moreover, 
a  large  proportion  of  each  kind  was  examined.  No  plague  bacilli  were 
found  in  the  cat  fleas,  1  only  in  85  of  the  human  fleas  was  infected,  and 
no  less  than  23  out  of  77  of  the  rat  fleas  harbored  plague  organisms. 

It  was  also  shown  that,  when  rats  in  the  course  of  an  epizootic  died 
of  plague,  the  pathological  features  manifested  in  their  bodies  corre- 
sponded to  those  exhibited  by  artificially  rat-flea-infected  animals,  and 
hence  it  was  inferred  that  in  nature  and  under  experimental  conditions 
the  animals  had  alike  succumbed  to  a  single  agency.  This  identity 
especially  related  to  the  site  in  which  buboes  arose,  that  in  both  instances, 
where  the  place  of  inoculation  could  be  observed  was  similar. 

Further  Observations.  —  A  study  of  mortality  statistics  shows  that 
the  greater  percentage  of  plague  occurs  in  the  autumn,  —  September 
and  October.  This  seasonal  occurrence  is  undoubtedly  due  to  climatic 
conditions,  moisture  and  cold  as  affecting  the  life  history  and  habitat 
of  the  rat  and  of  the  flea.  Blue  ^  reports  a  number  of  observations 
made  in  San  Francisco  indicating  modes  of  infection ;  thus  two  small 
boys  found  the  body  of  a  dead  rat  in  an  unused  cellar;  the  rat  was 
buried  with  unusual  funeral  honors  and  in  forty-eight  hours  both  were 

1  Blue,  Surgeon  Rupert,  1910.  Rodents  in  relation  to  the  transmission  of 
plague.  U.  S.  Pub.  Health  Bulletin.  The  rat  and  its  relation  to  the  pubUe 
health. 


282       MEDICAL  AND   ^  ETERINARY  ENTOMOLOGY 


taken  ill  with  bubonic  plague.  Again,  a  laborer  picked  up  a  dead  rat 
with  the  naked  hand  and  threw  it  into  the  bay.  He  was  taken  ill  with 
plague  three  days  later.  The  case  of  a  physician's  family  is  also  cited 
in  which  foul  odors  pervaded  their  second  story  flat  over  a  grocery  store. 
On  removing  the  wainscoting  around  the  plumbing  to  ascertain  the 
cause  of  the  odor,  two  rat  cadavers  were  found  in  the  hollow  wall.  In 
two  or  three  days  thereafter  the  two  members  of  the  family  who  used 
the  room  sickened,  one  dying  on  the  fifth  day  of  cervical  bubonic  plague. 
Blue  believes  that  the  removal  of  the  wainscoting  set  free  infected  rat 
fleas. 

A  most  illuminating  case  is  reported  in  the  U.  S.  Public  Health  Re- 
ports (Nov.  7,  1913,  p.  2356),  viz.  a  fatal  case  of  plague  occurred  in 
Manila  (P.  I.)  in  the  person  of  an  American,  editor  of  the  Manila  Daily 
Bulletin.  A  plague  rat  had  been  found  on  September  6  in  the  block 
adjacent  to  the  one  in  which  the  newspaper  offices  were  located.  The 
editor  was  admitted  to  the  hospital  September  19  and  died  at  the  Plague 
Hospital  three  days  later.  A  mummified  rat  was  found  in  the  desk  of 
the  late  editor,  together  with  live  fleas,  Xenopsylla  cheopis.  Both  the 
fleas  and  rat  revealed  bipolar  staining  organisms  and  inoculations  into 
healthy  laboratory  rats  produced  typical  cases  of  plague  terminating 
fatally. 

The  facts  that  the  mummified  rat  must  have  been  dead  at  least  two 
weeks  and  that  the  live  fleas  contained  plague  bacilli  causes  the  com- 
ment to  be  made  that  "these  facts 
furnish  strong  proof  that  plague 
might  be  introduced  into  a  country 
without  either  the  importation  of 
human  or  rat  cases  of  plague  and 
that  fleas  might  be  alone  con- 
cerned." 

How  the  Flea  Receives  and 
Transmits  Plague.  —  It  w^as  found 
by  the  Indian  Plague  Commission 
according  to  Fox  {loc.  cit.),  that  the 
average  capacity  of  a  flea's  stomach 
(Xenopsylla  cheopis)  was  .5  cubic 
millimeter  and  that  it  might  re- 
ceive as  many  as  5000  germs  while 
imbibing  blood  from  a  plague  rat. 
They  further  found  that  the  bacillus 
would  multiply  in  the  stomach  of  a 
flea  (Fig.  179)  and  that  the  per- 
centage of  fleas  with  bacilli  in  the  stomach  varied  with  the  season  of 
the  year.  In  the  epidemic  season  the  percentage  was  greatest  for  the 
first  four  days,  and  on  one  occasion  the  stomach  was  found  filled  with 
Bacillus  pestis  on  the  twentieth  day.     In  the  non-epidemic  season  no 


Fig.  179.  —  Showing  Bacillus  pestis  from 
the  intesfine  of  a  rat  flea,  Ceratophyllus 
fasciatus,  taken  from  a  plague  rat.  (Photo- 
graph by  Mitzmain.     Greatly  enlarged.) 


FLEAS  AND   LOUSE   FLIES  283 

plague  bacilli  were  found  in  the  stomach  after  the  seventh  day.  They 
also  found  that  in  the  epidemic  season  fleas  might  remain  infective  up 
to  fifteen  days,  while  in  the  non-epidemic  season  but  seven  days,  and 
in  the  latter  case  the  percentage  of  infection  in  animals  was  much  less 
than  in  the  epidemic  season.  They  showed  that  while  one  flea  was 
occasionally  able  to  carry  the  infection  this  was  not  usual.  It  was  found 
that  both  males  and  females  were  capable  of  transmitting  the  disease.  As 
to  the  manner  of  dissemination  the  Commission  found  bacilli  only  in  the 
stomach  and  rectum  and  never  in  the  salivary  glands  nor  body  cavity 
and  but  rarely  in  the  esophagus,  and  then  only  when  the  flea  was 
killed  immediately  after  feeding.  As  far  as  the  writer  knows  the  plague 
bacilli  have  not  been  demonstrated  on  mandibles,  i.e.  in  a  purely  soiled 
condition,  hence  this  fact  and  the  absence  of  the  bacilli  from  the  salivary 
glands  seems  to  preclude  the  possibility  of  direct  inoculation  by  the 
bite,  although  it  seems  quite  probable  that  plague  bacilli  might  also  be 
regurgitated,  particularly  when  the  flea's  stomach  is  overfull  and  thus 
be  injected  at  the  time  of  biting.  Very  recently  Bacot  and  Martin  ^ 
have  come  to  the  conclusion  that  plague  can  be  transmitted  during  the 
act  of  biting  when  a  temporary  blocking  or  obstruction  of  the  proventric- 
ulus  takes  place  causing  bacillus-laden  blood  to  be  forced  back  or  re- 
gurgitated into  the  wound,  thus  producing  infection. 

It  will  be  observed  that  when  a  flea  bites  it  commonly  ejects  feces 
and  partially  digested  blood  in  the  vicinity  of  the  bite.  It  has  been 
shown  that  an  emulsion  of  plague  flea  feces  placed  upon  the  wound 
produced  by  the  bite  induces  the  disease  in  the  animal,  provided  this 
is  done  within  twenty-four  hours  after  the  insect  has  bitten,  after  which 
time  the  wound  has  probably  healed  sufficiently  to  exclude  the  organ- 
isms. The  actual  inoculation  is,  therefore,  evidently  an  accidental 
process,  i.  e.  the  plague  bacilli  discharged  per  anum  are  rubbed  into  the 
bite  of  the  flea  either  by  the  insect  as  it  moves  about  or  by  the  person  in 
the  act  of  scratching,  —  many  persons  very  commonly  scratch  a  flea  bite 
until  it  bleeds.  This  method,  together  with  that  advanced  by  Bacot  and 
Martin,  probably  explains  the  flea's  role  in  the  dissemination  of  plague. 

Squirrels  and  Plague.  —  Plague  has  been  found  in  a  number  of 
species  of  rodents  other  than  rats,  notably  ground  squirrels  {Citellus 
beecheyi)  (Fig.  180).  In  California  the  disease  was  demonstrated  in 
ground  squirrels  under  natural  conditions  in  1908  according  to  McCoy. ^ 
According  to  this  author  at  the  time  of  his  writing  (1910)  about  a  dozen 
persons  had  contracted  the  disease  under  circumstances  that  pointed 
conclusively  to  squirrels  as  the  cause.  The  two  species  of  fleas  com- 
monly infesting  the  ground  squirrel  in  California  are  Ceratophyllus 
acutus  Baker  and   Hoplopsyllus  anomalus  Baker  of  which  the  former 

1  Bacot,  A.  W.,  and  Martin,  C.  J.,  1914.  Observations  on  the  mechanism 
of  the  transmission  of  pla^e  by  fleas.  Jonrn.  of  Hygiene.  Plague  Supple- 
ment III,  Jan.  14,  1914,  pp.  423-439. 

2  McCoy,  George  W.,  1910.  Bubonic  plague  in  ground  squirrels.  N.  Y. 
Med.  Journ.,  Oct.  1,  1910;  see  also  U.  S.  Public  Health  Bulletin,  No.  43. 


284       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


is  far  more  numerous.  McCoy  proved  the  first-named  species  a  carrier 
as  follows.  He  inoculated  a  ground  squirrel  subcutaneously  with  a 
broth  culture  of  B.  pestis  derived  from  a  human  case  of  plague.  This 
squirrel  died  on  the  fifth  day,  but  three  days  before  its  death,  100  fleas, 
C.  acutus,  were  put  in  the  cage  with  it.     The  dead  animal  was  removed 

from  the  cage  while  warm,  and  27  live 
fleas  taken  from  its  body.  Smears 
made  of  the  crushed  bodies  of  two  of 
these  fleas  showed  an  abundance  of 
pest-like  bacilli  in  each.  The  remain- 
ing 25  fleas  were  put  in  a  clean  cage 
with  a  healthy  squirrel.  This  animal 
died  of  subacute  plague  10  days  later, 
the  buboes  being  in  the  region  of  the 
median,  posterior  inguinal  and  pelvic 
glands.  A  pure  culture  of  B.  yestis 
was  obtained  from  the  liver.  McCoy 
rightfully  concludes  that  the  experi- 
ment is  conclusive  in  showing  that 
C.  acutus  may  convey  plague  from  a 
sick  to  a  healthy  squirrel.  The 
squirrels  used  in  the  experiment  were 
kept  in  quarantine  for  at  least  a 
month  prior  to  their  being  used,  which 
was  necessary  to  exclude  any  naturally 
infected  ones.  McCoy  found  the 
bacilli  in  squirrel  flea  feces  four  days 
after  removal  of  the  fleas  from  the  host. 
Flea  Control.  {A)  Fleas  in  the 
House.  —  The  commonest  household 
flea  in  Europe  is  Pulex  irritans,  the 
human  flea,  also  predominating  in 
California,  while  Ctenocejjhalus  canis, 
the  cat  and  dog  flea,  is  commonest  in 
the  eastern  portion  of  the  United 
States.  Both  species  are  very  often 
present  at  the  same  time,  and  both  species  infest  cats  and  dogs ;  as  a 
matter  of  fact  they  have  a  wide  range  of  host  animals.  Unless  house 
dogs  and  cats  are  very  carefully  groomed  and  repeatedly  washed  with 
efficient  insecticides  the  presence  of  these  animals  will  always  be  a  source 
of  many  fleas. 

In  treating  a  house  for  fleas  it  must  be  borne  in  mind  that  the  larvae 
develop  primarily  in  the  crevices  of  the  floors,  under  carpets  and  mat- 
tings. The  old-fashioned  tacked-down  carpets  and  mattings,  still  so 
commonly  used,  must  be  done  away  with,  unless  an  insecticide  is  used, 
which  when  applied  to  carpets  in  wetting  quantities  does  not  injure 


Fig.  180.  —  Tv/o  varieties  of  the  com- 
mon "digger"  ground  squirrel  of  the 
Pacific  Coast.  Tlie  squirrel  at  left  is 
the  Do\iglas  ground  squirrel  {Ciicllus 
dcuglasi) ,  found  along  the  coast  north 
of  San  Francisco  Bay  ;  the  one  to  the 
right  is  the  California  ground  squirrel 
(Citellus  beecheyi  heecheyi),  the  com- 
mon ground  squirrel  of  the  interior 
valleys  and  a  carrier  of  bubonic 
plague.  (Photo  by  University  of 
California  Museum  of  Vertebrate 
Zoology.)     X  .16. 


FLEAS  AND   LOUSE   FLIES  285 

the  fabric.  Benzine  is  often  recommended,  but  its  dangers  must  be 
considered,  both  before  and  after  applying.  The  writer  does  not 
undertake  the  responsibihty  of  recommencHng  benzine  for  this 
purpose.  With  the  removal  of  carpets  and  matting,  floors  can 
easily  be  moistened  with  an  oil  mop,  using  kerosene.  All  parts 
of  the  floor  in  all  parts  of  the  house  must  be  reached.  The 
odor  of  kerosene  is  not  particularly  disagreeable  and  at  all  events 
soon  disappears.  Treatment  should  be  repeated  at  least  once  every 
three  or  four  weeks  during  the  flea  season.  This  method  of  treatment 
has  invariably  given  good  results.  Dr.  L.  O.  Howard  recommends  a 
free  sprinkling  of  pyrethrum  powder  as  the  easiest  remedy  to  be  applied, 
or  washing  the  floors  with  hot  soapsuds.  Dr.  Henry  Skinner  has 
successfully  destroyed  fleas  in  a  badly  infested  room  by  sprinkling  the 
floor  liberally  with  about  five  pounds  of  flake  naphthalene  and  closing 
the  room  for  twenty-four  hours.  The  acrid  fumes  destroyed  the  fleas 
and  inflicted  no  material  injury  (Felt).^ 

(B)  Treatment  of  dogs,  cats  and  other  domesticated  animals  kept  in  or 
near  the  house  is  essential  to  the  control  of  fleas.  Mats  on  which 
house  pets  sleep  should  be  shaken  out  over  kerosene,  soapsuds  or  a 
fire  every  few  days  in  order  to  destroy  flea  eggs  which  have  fallen  from 
the  host  when  it  shakes  itself.  The  sleeping  quarters  should  be  liberally 
dusted  with  California  buhach  or  pyrethrum  powder.  Fleas  also  breed 
abundantly  in  loose  dry  manure  and  debris  in  stables,  chicken  houses, 
yards,  etc.  A  spray  of  high  flash  point  fuel  oil  is  very  useful  under  these 
circumstances.  The  best  method  to  keep  cats,  dogs,  monkeys,  etc., 
free  from  fleas  is  to  give  them  frequent  baths  with  warm  water  to  which 
enough  creolin  is  added  to  make  a  2  per  cent  solution.  If  the  animal 
is  dipped  in  the  solution,  the  eyes  should  be  quickly  rinsed  or  sponged 
with  clear  water. 

Animals  infested  with  fleas  may  also  be  liberally  dusted  with  Cali- 
fornia buhach  or  pyrethrum  powder.  The  dust  rubbed  well  into  the 
hair  causes  the  fleas  to  drop  off  in  a  stupefied  condition,  when  they  can 
be  brushed  up  and  burned.  If  the  latter  is  not  done  the  insects  soon 
revive  and  go  about  their  "  business  "  as  usual. 

(C)  Rat  Control.  —  Not  only  are  rats  an  object  of  control  because 
of  their  menace  to  health  but  they  are  also  injurious  in  many  other 
ways.  According  to  Lantz  ^  there  are  several  species  of  house  rats 
(Fig.  181),  among  them  the  black  rat  {Mus  rattns),  the  roof  rat  (Mus 
alexandrinus)  and  the  brown  rat  {Mus  norvegicus),  of  which  the  last 
named  species  is  by  far  the  commonest.  All  of  these  species  were 
imported  from  the  Old  World.  The  habits  of  house  rats,  except  the 
roof  rat,  are  generally  quite  similar,  hence  methods  of  control  are  alike 
applicable,  and  manifestly  the  control  of  the  host  involves  the  control 

1  Felt,  E.  P.,  1909.      Control   of  household  insects.      Museum  Bull.  129. 
N.  Y.  State  Museum,  Albany,  N.  Y. 

2  Lantz,  David  E.,   1909.     How  to  destroy  rats.     U.  S.  Dept.  of  Agric, 
Farmers'  Bull.  369. 


286       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


of  the  flea.  Rucker  ^  has  well  said,  "  Rodent  extermination  is  a 
problem  with  difficulties  arising  from  the  animal's  highly  developed 
regard  for  self-preservation.  In  the  main,  the  rat  requires  two  condi- 
tions for  life.  He  needs  plentiful  food  and  places  suitable  for  nesting 
and  breeding.  Eliminate  either  of  these  elements  and  you  drive  away 
your  rats.  Yet  the  problem  remains  far  more  difficult  than  shown  in 
the  simple  terms  of  the  above  equation.  The  fabulous  speed  at  which 
rats  multiply  will  baffle  all  but  the  most  determined  and  efflcient  efforts 
to  exterminate  them.  Under  normal  conditions  each  female  bears  three 
litters  a  year  and  each  litter  produces  ten  young.  Under  conditions 
ideally  favorable  it  Tias  been  computed  that  one  pair  of  rats  will,  in 


Fig.  181. 


House  rats,     (a)  AIus  rattus,  the  black  rat ;    (6)  Mus  norvegicus,  the  brown 
rat;    (c)   AIux  alexandrinus,  the  roof  rat.       X  .13. 


five  years,  provided  all  can  live  so  long,  increase  to  940,369,969,152. 
Such  a  result  is,  of  course,  impossible  in  nature.  .  .  .  The  size  and 
frequency  of  rodent  litters  decreases  proportionately  with  every  cutting 
off  of  food  supplies.  Separate  the  rat  from  his  pabulum  and  he  will 
not  breed  so  freely  nor  so  often  as  when  he  is  well  fed.  Destroy  rat 
habitations  and  make  it  impossible  for  them  to  find  new  nesting  places, 
and  breeding  will  virtually  cease,  since  the  unsheltered  progeny  can  no 
longer  survive,  and  since  the  starving  rats  are  driven  to  cannibalism  in 
the  struggle  for  existence." 

Rat  control  may  be  accomplished  by  the  proper  combination  of 
the  following  methods  depending  upon  circumstances,  (a)  Rat  proofing 
is  by  far  the  most  important  method.  This  is  done  by  the  use  of  con- 
crete in  building  foundations  and  floors  to  stables,  corncribs,  poultry 
houses,  outbuildings,   dwellings,  etc.       Cement  construction  requires 

1  Rucker,  William  Colby,  1910.  "Rodent  extermination"  in  U.  S.  Public 
Health  BuU.  on  "The  rat  and  its  relation  to  the  public  health,"  pp.  153-162. 


FLEAS  AND   LOUSE   FLIES  287 

comparatively  little  skill,  is  not  expensive  and  is  becoming  an  im- 
portant factor  in  building  the  rat  out  of  existence,  (b)  Cutting  off  the 
food  supply  essentially  means  (1)  proper  disposal  of  garbage,  i.e.  by 
burning  the  same  speedily  or  placing  it  in  covered  metal  garbage  cans ; 
(2)  cremation  of  slaughter  house  refuse ;  (3)  use  of  heavy  wire  netting 
for  the  protection  of  foodstuffs,  feed  bins,  etc.  (c)  Natural  enemies 
of  the  rat  where  otherwise  not  objectionable  should  be  protected. 
Among  the  hawks,  the  red-tailed  species  {Buteo  borealis)  is  said  to  be 
most  efficient;  among  the  owls,  the  barn  owl  {Aluco  pratincola)  is  of 
greater  importance ;  skunks  and  weasels  are  good  ratters ;  a  well- 
trained  fox  terrier  is  a  very  useful  adjunct  to  every  farm,  (d)  Rat 
trapping  is  best  accomplished  by  means  of  the  snap  traps.  These 
should  be  well  smoked  and  baited  with  fried  bacon  securely  tied  to  the 
trigger.  Each  time  before  using,  it  is  well  to  scald  the  trap  with  hot 
water  and  "  sizzle  "  the  bait  with  a  lighted  match  or  torch,  (e)  Rat 
poisoning  is  ordinarily  dangerous  to  the  life  of  domesticated  animals 
and  children.  Among  the  poisons  commonly  used  are  (1)  phosphorus 
paste  prepared  by  mixing  crude  phosphorus  over  heat  with  glucose, 
cheese,  meat,  etc.  Danger  from  combustion  must  be  borne  in  mind. 
(2)  Arsenic  paste  consists  of  an  arsenious  acid  (powdered  white  arsenic) 
combined  with  oatmeal,  cheese,  toast,  etc.  (3)  Strychnine  crystals 
(strychnine  sulphate)  may  be  placed  in  pieces  of  cheese  or  meat  and 
put  in  the  rat  runways.  Extreme  caution  must  he  exercised  in  the  use 
of  rat  poisons  oiving  to  danger  to  human  life.  State  laivs  must  be  regarded 
in  this  respect  as  ivell. 

(D)  Squirrel  Control.  —  The  most  destructive  as  well  as  most  dan- 
gerous species  (as  referred  to  public  health)  are  the  "  digger  "  ground 
squirrels  of  the  genus  Citellus  (Fig.  180) .  These  squirrels  live  in  colonies, 
ordinarily,  and  dig  an  extensive  meshwork  of  connecting  burrows.  Their 
food  consists  of  grain,  seeds  and  fruit  and  is  stored  for  the  winter. 
The  young  are  usually  born  in  March  and  April  in  California  and  their 
litters  number  from  five  to  ten.  Three  general  methods  of  control  are 
commonly  employed.  (1)  Shooting  and  trapping.  Shot  guns  carry- 
ing No.  7  or  8  shot  are  best  employed,  and  chain  traps  are  the  best  if 
trapping  is  to  be  done  at  all.  (2)  Suffocation  in  the  burrows  may  be 
accomplished  by  either  flooding  with  water  or  by  the  introduction  of 
poisonous  gases.  Carbon  bisulphide  is  the  most  efficient  agent  and  is 
commonly  employed.  The  following  account  of  this  gas  and  its  use  is 
based  largely  on  the  work  of  Simpson.^ 

Carbon  bisulphide  is  obtained  commercially  in  the  form  of  a  liquid, 
which  is  readily  vaporized  or  is  converted  chemically  into  other  gases. 
While  it  is  the  most  useful  material  as  applied  against  ground  squirrels 
there  are  some  objectionable  features,  namely,  it  is  very  inflamniable, 
must  be  kept  in  tightly  closed  containers  and  under  certain  conditions 

1  Simpson,  F.,  1911.  Ground  squirrel  eradication.  California  State 
Board  of  Health  BuUetin,  No.  8,  Vol.  6,  pp.  507-512. 


288       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

may  explode;  furthermore  during  the  dry  season  if  "exploded  "  in  the 
burrow  there  is  danger  of  igniting  dry  grass  or  other  inflammable  ma- 
terial in  the  vicinity.  If  handled  with  as  much  care  as  gasoline,  for 
example,  the  danger  is  not  so  great  after  all.  The  advantages  in  its 
use  are,  that  it  is  readily  converted  into  a  poisonous  gas,  diffuses  quickly, 
destroys  life  rapidly  and  can  be  used  most  readily  during  the  rainy 
season  when  green  food  is  abundant,  thus  preventing  the  most  successful 
use  of  poisoned  grain. 

The  bisulphide  may  be  used  in  one  of  two  ways,  namely,  in  the 
simple  liquid  condition  by  evaporation,  when  there  will  be  but  little 
waste,  or  it  may  be  used  by  igniting  or  exploding  it.  In  either  case 
it  is  suggested  that  from  one  to  three  days  prior  to  the  application  of 
the  poison  all  squirrel  burrows  in  the  area  to  be  treated  should  be  stopped 
with  earth.  The  holes  found  opened  indicate  the  burrow  in  which 
there  are  squirrels. 

The  method  of  applying  the  bisulphide  by  the  ignition  method  is  as 
follows :  To  handle  a  large  area  to  best  advantage  two  men  working 
together  is  suggested.  "  One  man  is  provided  with  a  supply  of  '  waste,' 
'  sacking,'  or  other  absorbent  material,  divided  into  a  number  of  small 
balls  about  half  the  size  of  the  fist.  The  bisulphide  is  carried  in  an 
ordinary  one  gallon  oil  can,  and  refilled  from  time  to  time  from  a  supply 
kept  in  a  cool  place  out  of  the  sun.  He  is  supplied  with  matches.  His 
'  pardner '  carries  a  mattock  or  long-handled  shovel.  On  arrival  at 
an  opened  squirrel  burrow,  a  ball  of  '  waste  '  is  saturated  with  two 
ounces  of  bisulphide,  dropped  deeply  in  the  burrow  and  then  a  match 
applied.  After  a  moment's  time  the  man  with  the  shovel  stops  with 
earth  this  burrow  and  all  other  burrows  near  from  which  the  gas  es- 
capes. On  subsequent  inspection  of  the  field  all  opened  burrows  will 
indicate  holes  lacking  effective  treatment."  Exploding  the  bisulphide 
thus  causes  considerable  gas  to  escape,  but  "  the  ignition  produces  a 
violent  chemical  reaction  and  as  a  result  sufficient  oxygen  from  the  air 
combines  with  the  carbon  and  sulphur  elements  to  produce  a  volume  of 
gas  three  times  that  which  the  original  bisulphide  would  produce  on 
evaporation.  The  gases  produced,  carbon  dioxide  and  sulphur  dioxide 
in  the  proportion  of  1  to  2,  seem  just  as  eft'ective  as  bisulphide  of  carbon, 
and  the  method  is  superior  in  that  the  explosion  produced  drives  these 
gases  deeply  into  the  burrow."  Two  ounces  or  60  cc.  of  the  bisulphide 
produces  about  twelve  gallons  of  gas. 

To  use  the  gas  unexploded  simply  omit  igniting  it. 

A  much  cheaper  and  more  efficient  method  of  destruction  with 
carbon  bisulphide  has  been  devised  by  Long  ^  and  others,  namely,  a 
pump  with  a  device  measuring  the  quantity  of  liquid,  and  serviceable 
at  all  seasons  of  the  year.  The  pump  loaded  with  nine  pints  of  bisulphide 
weighs  twenty-five  pounds.     Refined  bisulphide  should  be  used  in  this 

1  Long,  John  D.,  1912.     A   squirrel  destructor.      U.  S.  Pub.  Health  Re- 
ports.    No.  98.     (Reprint.) 


FLEAS  AND  LOUSE   FLIES 

pump  because  the  metal  is  rapidly  corroded  by  the  crude  material. 
The  refined  bisulphide  is  said  to  contain  99.92  per  cent  carbon  bisulphide 
and  0.08  per  cent  sulphur  in  solution  and  no  hydrogen  sulphide  nor 

sulphuric  acid. 

Onlv  one  half  ounce  (15  cc.)  is  required  for  each  hole  against  two 
ounces  by  the  ignition  method,  and  it  is  claimed  that  the  men  using  the 
piimp  have  been  able  to  treat  from  200  to  250  holes  with  each  gallon 
of  the  bisulphide,  against  50  to  60  holes  per  gallon  with  the  waste  ball 
method  above  described.  The  cost  of  the  apparatus  is  about  $10  per 
machine  and  the  cost  per  acre  of  treatment,  going  over  the  ground 
twice,  is  estimated  at  20  cents  with  ten  squirrel  holes  per  acre. 

The  use  of  the  apparatus  is  thus  described  (see  Fig.  182)  :  "  Insert 
the  hose  in  the  squirrel  hole  at  least  one  foot ;  then  run  one  half  ounce  of 
bisulphide  from  the  reservoir  into  the  measuring  cup ;  then  turn  cock 
with  handle  down  to  allow  liquid  to  run  into  vaporizing  chamber,  mean- 
while covering  the  hole  with  dirt  with  the  aid  of  a  mattock.  Then 
pump  thirty  strokes  (in  cold  weather  use  one  ounce  with  forty  strokes). 
This  equals  12  cubic  feet  or  1.5  per  cent  bisulphide  gas.  Withdraw 
the  hose,  close  hole  opening  by  stamping  in  the  dirt  with  the  heel  and 
proceed  to  the  next  hole." 

(3)  Squirrel  Poisoning.  —  In  the  use  of  poison  for  squirrels  several 
important  factors  must  be  considered,  namely,  it  must  not  be  distasteful 
to  the  rodents  and  must  enter  the  circulation  readily ;  the  poison  must 
be  applied  to  food  readily  eaten  by  the  squirrels  and  at  a  time  when 
the  usual  green  food  is  at  its  minimum .  It  has  been  found  that  strychnia 
sulphate  (the  pure  alkaloid  should  not  be  used)  is  most  effective,  but  the 
bitter  taste  must  in  some  manner  be  concealed.  The  use  of  whole 
barley,  i.e.  threshed  but  still  retaining  the  husk,  is  recommended  by 
the  U.  S.  Biological  Survey.  In  this  form  the  barley  is  not  eaten  by 
birds  and  is  most  acceptable  to  the  squirrels ;  it  is  also  cheaper  m  this 
form.  Wheat  is  very  acceptable  to  the  rodents  but  when  poisoned  is 
very  destructive  to  birds,  particularly  quail,  doves  and  other  grain  eaters. 
Piper  of  the  U.  S.  Biological  Survey  has  devised  a  formula  whereby 
the  bitter  taste  of  the  strychnine  is  delayed  about  two  niinutes,  thus 
enabling  the  squirrel  to  fill  its  cheek  pouches  before  the  bitter  taste  is 
noted,  —  the  formula  is  as  follows  : 

Barley  (recleaned) 18  pounds 

Strychnine  sulphate 1  ounce 

Soda 1  ounce 

Saccharine 1  dram 

Thin  soupy  starch  paste 1  P^^t 

Corn  sirup  (Karo  or  equal) 2  oz. 

Dissolve  the  strychnine  in  hot  water ;  thicken  with  starch  to  thin 
soupy  consistency.  Mix  the  soda  in  ^  pint  hot  water ;  stir  into  poisoned 
starch.  When  effervescence  ceases,  add  sirup  and  saccharine,  apply  to 
grain  and  continue  mixing  until  mixed  and  dry. 


290       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


FLEAS  AND  LOUSE   FLIES 


291 


According  to  Simpson  (loc.  cit.)  grain  poisoned  with  strychnine 
placed  in  proper  containers  will  retain  its  poisonous  character  and  re- 
main effective  for  an  indefinite  period,  but  heavy  dews  and  rain  may 
remove  the  poison  and  destroy  the  efficiency  of  the  grain  in  this  respect. 
Therefore  this  method  is  applicable  during  the  dry  season  only.  The 
above  author  states  that  thirty  kernels  in  the  cheek  pouches  of  squirrels 
rapidly  prove  effective,  whereas  sixty  or  ninety  or  more  in  the  stomach 
may  produce  only  a  few  convulsions  and  recovery  ensues.  He  says, 
"  This  fact  should  be  remembered  in  placing  poison,  for  by  scattering 
the  grain  a  few  kernels  here  and  there  near  the  burrow  the  squirrel  is 
induced  to  store  the  grain  temporarily  in  the  cheek  before  a  sufficient 
quantity  is  obtained  for  a  meal.  ..."  It  should  be  scattered  where 
the  squirrel  is  accustomed  to  find  food,  and  will  probably  be  found  most 
efficient  if  placed  early  in  the  morning,  between  the  hours  of  3  a.m.  and 

7  A.M. 

The  Chigoe  Flea  (Sarcopsylla  penetrans  Linn.),  known  as  "jigger," 
"  chigger,"  "  chique,"  or  "  sand  flea,"  is  a  tiny  burrowing  flea  (Fig. 
183)  found  in  the  tropical  and  antitropical  regions  of  North  and  South 
America,  also  in  the  West  Indies  and  Africa.  Its  introduction  into 
Africa  is  said  to  have  occurred  as  late  as  1872.  The  chigoe  is  a  reddish 
brown  flea  about  1  mm.  in  length, 
except  that  the  impregnated 
female  may  become  as  large  as  a  ^-^ 

small  pea,  the  head  is  proportion- 
ately large,  there  are  no  ctenidia 
on  the  head  and  thorax,  the  palpi 
are  four-segmented  and  the  mouth 
parts  are  conspicuous.  The  adult 
fleas  are  intermittent  feeders  but 
adhere  closely  to  the  host,  the 
female  when  impregnated  proceeds 
to  burrow  into  the  skin  of  the 
host.  The  eggs  are  deposited 
either  in  the  ulcer  or  drop  to  the 
ground  when  discharged  from  the 
body  of  the  female.  The  larvse 
which  emerge  in  a  few  days  from 
the   eggs    are  typical   flea    larvse. 

Those  hatching  in  the  ulcer  drop  to  the  ground  to  develop  under  condi- 
tions similar  to  those  having  hatched  on  the  ground.  The  larval  period 
under  favorable  conditions  probably  requires  not  more  than  ten  to  four- 
teen days  and  the  cocoon  or  pupal  period  about  a  like  number  of  days. 

Pathogenesis.  —  The  chigoes  commonly  attack  the  bare  feet,  these 
being  nearest  the  ground,  infesting  the  skin  between  the  toes,  and  the 
soles ;  no  part  of  the  body  is  really  exempt  from  attack.  The  burrow- 
ing female  flea  causes  extreme  irritation,  the  area  surrounding  the  flea 


Fig.   183.  —  The  chigoe  flea,  Dermafophilus 
penetrans.     X  35. 


292       MEDICAL  AND   VETERINARY   ENTOMOLOGY 

becomes  charged  with  pus,  producing  a  distinct  elevation.  The  ulcera- 
tions due  to  the  presence  of  numerous  chigoes  become  confluent  and 
very  grave  results  are  often  involved.  Wellman  attributes  the  com- 
monly observed  auto-amputation  of  toes  to  the  work  of  the  chigoe. 

Treatment  and  Control.  —  Where  the  chigoe  flea  commonly  occurs, 
the  habitations  of  humans  and  of  domesticated  animals  (for  these  are 
also  subject  to  attack)  must  be  kept  clean  and  free  from  dust,  the  floors 
may  be  swept  up  with  a  liberal  sprinkling  of  naphthalene  flakes,  or  with 
fresh  buhach  orpyrethrum  powder.  Where  possible,  kerosene  treatment 
should  be  applied  as  described  above  for  other  fleas.  Walking  in  bare 
feet  should  be  avoided. 

Parts  of  the  body  attacked  by  the  fleas  should  receive  immediate 
attention.  The  insect  can  be  removed  quite  easily  by  means  of  a  sterile 
needle  or  very  fine  pointed  knife  blade.  The  wounds  caused  by  this 
treatment  are  then  carefully  dressed  and  allowed  to  heal.  Applications 
of  turpentine  or  other  remedies  serve  to  kill  the  fleas,  which  are  then 
discharged  by  ulceration. 

The  Hen  Flea,  Echidnophaga  (Xestopsylla)  gallinacea,  also  known 
as  the  "  stick  tight  "  of  poultry,  is  one  of  the  worst  poultry  pests  in 

many  parts  of  subtropical  America 
(Fig.    184).     It   commonly    attacks 

#  poultry    of    all    kinds,    cats,    dogs, 

horses  and  even  humans.  Osborn 
{loc.  cit.)  states  that  this  species 
differs  from  the  foregoing  "in  having 
the  hind  angles  of  the  metathoracic 
scales  angled  instead  of  rounded 
'/,*     <  and   the   eyes  and  antennse  in  the 

'^  '*'*^^  posterior  half  of   the  head.     It   is 

^■^  from  1  to  1^  mm.  in  length." 

Before  copulation  both  sexes 
are  active,  hopping  about  nauch  as 
do  other  species  of  fleas.     Shortly 

Fig.   1M. -Echiduophaoa  gallinacece,  the     ^^^^\  feeding    begins     the     females 

chicken  flea  or  stick  tight.    X  25.  attach  themsclvcs  firmly  to  the  skin 

of  the  host  and  begin  to  burrow. 
At  this  time  the  sexes  are  in  copulation.  The  burrowing  females 
deposit  their  eggs  in  the  ulcers  which  have  been  produced  by  the  in- 
festation. The  larvse  crawl  out  of  the  ulcer  and  drop  to  the  ground, 
where  they  grow  rapidly,  under  favorable  conditions,  feeding  on  ni- 
trogenous matter,  dry  droppings,  etc.  The  full-grown  larva,  which 
is  not  unlike  other  flea  larvae,  is  about  4  mm.  in  length,  having  reached 
this  stage  in  evidently  about  two  weeks.  The  larva  then  spins  a 
cocoon,  pupates  and  in  about  two  Aveeks  emerges  as  a  full-developed 
flea.  The  life  history  requires  about  four  weeks,  more  or  less,  based 
on  rather   crude   observations.     The   writer   believes   also  that  eggs 


FLEAS  AND  LOUSE   FLIES  293 

are  deposited  in  the  dust  or  dry  droppings  of  poultry,  or  in  old  nests, 
etc. 

The  fleas  are  most  likely  to  attack  the  skin  around  the  eyes  or  the 
anus  or  other  bare  spots.  The  ulceration  and  wart-like  elevations 
around  the  eyes  often  become  so  aggravated  that  blindness  results, 
the  host  is  unable  to  find  its  food  and  death  results. 

To  control  the  hen  flea  a  thorough  cleaning  up  is  very  necessary. 
The  debris,  dust,  etc.,  must  either  be  burnt  or  treated  liberally  with 
kerosene  right  in  the  yard  so  that  the  fleas  do  not  become  distributed 
while  carrying  away  the  refuse.  The  writer  recommends  that  the  yards 
and  coops,  particularly  crevices,  be  thoroughly  scalded  out  by  liberal 
applications  of  boiling  water  or  by  the  use  of  kerosene  or  a  light  fuel  oil 
applied  with  a  spray  pump.  Coops  and  yards  which  have  crude  oil 
floors  are  comparatively  free  from  fleas  and  other  parasites  if  otherwise 
kept  in  good  condition.  The  hot  water  or  oil  treatment  must  be  re- 
peated once  every  three  or  four  weeks  during  the  flea  season.  The  use 
of  sheep  dips,  carbolic  acid  sprays,  etc.,  does  not,  as  a  rule,  give  good 
results  in  controlling  chicken  fleas. 

In  addition  to  the  above  treatment  infested  chickens  must  also  receive 
attention  in  order  to  destroy  the  ovulating  female  fleas.  This  may  be 
done  by  dipping  the  birds  in  a  5  per  cent  solution  of  Zenoleum,  Kreso 
or  even  Creolin.  The  use  of  naphthalene  flakes  in  the  nests  is  recom- 
mended or  if  this  seems  undesirable  a  liberal  layer  of  slaked  lime  in  the 
bottom  of  the  nest  may  be  substituted. 

B.   Louse  Flies  and  Forest  Flies 
Order  Diptera,  Family  Hippoboscidce 

Characteristics  of  Hippoboscidae.  —  The  family  Hippoboscidae  is 
characterized  by  Williston  as  follows :  "  Head  flattened,  usually  at- 
tached to  an  emargination  of  the  thorax;  face  short;  palpi  wanting; 
antennae  inserted  in  pits  or  depressions  near  the  border  of  the  mouth; 
apparently  one  jointed,  with  or  without  a  terminal  bristle  or  long  hairs. 
Eyes  round  or  oval,  sometimes  very  small ;  ocelli  present  or  absent. 
Thorax  flattened,  leathery  in  appearance ;  scutellum  broad  and  short. 
Halteres  small  or  rudimentary.  Abdomen  sac-like,  leathery  in  appear- 
ance, the  sutures  indistinct,  legs  short  and  strong,  broadly  separated 
by  the  sternum;  tarsi  short;  claws  usually  strong  and  dentated; 
empodia  usually  present.  Wings  present  or  absent.  .  .  .  They  are 
all  parasitic  in  the  adult  stage  upon  birds  or  mammals.  The  larvae  are 
pupiparous,  but  pass  nearly  the  whole  of  this  stage  within  the  abdomen 
of  the  parent,  being  extruded  when  nearly  ready  to  transform  into  the 
mature  fly."  The  mouth  parts  are  tubular  and  are  fitted  for  sucking 
blood.  The  species  occurring  on  birds  are  included  in  the  genera 
Olfersia  and  Ornithomyia,  which  according  to  Osborn  are  distinguished 


294       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


V 


in  that  the  former  has  two  teeth  under  each  claw  and  has  no  ocelli. 
The  most  important  species  is  the  sheep  tick  or  sheep  louse  fly,  Melopha- 
gus  ov'imis  Linn. 

The  Sheep  "  Tick,"  Melophagus  ovinus  Linn.  (Fig.  185),  is  a  wingless 
species,  reddish  brown  in  color,  about  5-7  mm.  in  length.  The  head  is 
short  and  sunken  into  the  thorax,  the  body  is  sac-like,  leathery  and  spiny. 
Life  History.  —  The  young  of  the  sheep  tick  leave  the  body  of  the 
female  ready  to  pupate.  The  extruded  pupa  (Fig.  185)  during  the 
course  of  a  few  hours  becomes  chestnut-brown  in  color,  the  secretion 
with  which  it  is  covered  hardens  and  serves  to  glue  the  pupa  firmly 

to  the  Avool  of  the  sheep.  The 
pupse  are  commonly  found  on  in- 
fested sheep  in  the  region  of  the 
shoulders,  thighs  and  belly.  Pupse 
may  be  found  on  sheep  at  all  times 
of  the  year,  though  the  time  re- 
quired for  development  in  the  win- 
ter is  longer  than  in  the  summer. 
Swingle  ^  who  has  carried  on  most 
careful  observations  on  this  insect 
states  that  pupse  require  from  nine- 
teen to  twenty-three  days  to  hatch 
in  the  summer,  whereas  nineteen  to 
thirty-six  days  are  required  during 
the  winter  on  sheep  kept  in  the 
barn  and  probably  forty  to  forty-five 
days  on  sheep  out  of  doors.  The  time  required  for  the  females  to  reach 
sexual  maturity  is  from  fourteen  to  thirty  days  and  over,  when  they 
begin  extruding  young  at  the  rate  of  one  about  every  seven  or  eight 
days.  Swingle  regards  about  four  months  as  the  average  life  of  a  sheep 
tick  and  that  from  10  to  12  pupae  are  deposited  on  an  average. 

The  whole  life  of  the  tick  is  spent  on  the  host ;  when  oft'  the  sheep 
the  insects  die  in  from  two  to  eight  days,  most  of  them  dying  in  about 
four  days. 

Pathogenesis.  —  The  presence  of  a  few  louse  flies  on  the  bodies  of 
sheep  does  not  materially  affect  them.  Ordinarily  the  presence  of  the 
insect  is  indicated  by  the  fact  that  the  animal  rubs  itself  vigorously, 
bites  the  wool  and  scratches.  Badly  infested  animals  show  emaciation 
and  general  unthriftiness. 

Control.  — ■  Since  the  principal  time  for  migration  from  the  sheep 
to  the  lambs  is  at  shearing  when  the  insects  are  taken  off  the  hosts  with 
the  wool,  it  is  wise  to  take  particular  pains  at  this  time  to  store  the  wool 
at  some  distance  from  the  lambs.  Inasmuch  as  the  ticks  die  within  a 
week  when  away  from  the  host,  and  cannot  well  crawl  any  great  dis- 

1  Swingle,  Leroy  D.,  1913.  The  life  history  of  the  sheep-tick,  MelophU' 
gus  ovinus.     Univ.  of  Wyoming  Agr.  Exp.  Sta.  Bull.  No.  99. 


Fig.  185.  —  The  sheep  tick  or  louse  fly, 
Melophagus  ovinus.  Pupa  (left) ,  adult 
(right).     X4.5. 


FLEAS  AND   LOUSE  FLIES 


295 


tance,  the  above  suggestion  is  well  worth  considering.  Swingle  states 
that  "  a  sheep  free  from  ticks  can  be  kept  for  months  beside  a  heavily 
infested  one  with  a  tight  partition  only  three  feet  high  between  them 
without  becoming  infested.  ...  A  bunch  of  females  placed  in  the 
wool  of  a  sheep  will  be  found  in  practically  the  same  place  for  two  days. 
Males,  however,  are  more  inclined  to  migrate."  A  flock  of  sheep  once 
freed  from  ticks  can  therefore  be  kept  clean  unless  infested  animals  are 
introduced. 

The  writer  has  reasons  to  doubt  the  efficiency  of  the  usual  sheep  dips 
such  as  "  lime  and  sulphur  "  and  tobacco  decoctions  in  the  destruction 
of  the  sheep  tick,  however,  other  dips,  such  as  Kreso,  Zenoleum  and 
Chloronaphtholeum,  if  used  as  directed  for  sheep  scab  mites  will  kill  the 
"  ticks  "  but  not  the  pupse.  The  time  for  the  second  dipping  is  governed 
by  the  life  history  of  the  parasite,  hence  in  warm  weather  (dipping  for 
ticks  is  best  done  in  the  autumn),  the  second  dipping  should  take 
place  in  about  twenty-four  days  after  the  first. 

No  doubt  a  liberal  use  of  buhach  or  pyrethrum  powder,  particularly 
as  a  winter  treatment,  would  prove  beneficial. 

The  louse  fly  of  the  deer  is  Lipoptena  depressa  Say  (Fig.  186),  an 
exceedingly  common  parasite  of  the  deer.  This  species  is  smaller  than 
Melophagus  ovinus,  other- 
wise similar ;  it  is  wingless 
when  found  on  the  host, 
but  has  well-developed 
filmy  wings  which  are 
evidently  lost  later  on 
(Fig.  186).  These  para- 
sites have  been  found  in 
chains,  three  or  four  at- 
tached to  each  other,  the 
first  tick  drawing  blood 
from  the  host,  the  second 
wdth  its  proboscis  thrust 
into  the  abdomen  (dor- 
sally)  of  the  first,  the  third  drawing  on  the  second 
last  most  lucky  individual. 

The  forest  fly  or  louse  fly  of  the  horse  is  Hippohosca  equina  Linn. 
This  species  is  quite  large  (length  8  mm.),  is  winged  and  a  fairly  good 
flier.  It  is  common  in  many  parts  of  the  world  but  occurs  rather  in- 
frequently in  America.  The  damage  which  it  does  would  depend  en- 
tirely on  its  abundance. 


FiCx.  186.  —  Louse  fly  of  the  deer,  or  deer  tick  {Lipop- 
tena  depressa),  showing  wingless  and  winged  form. 
X  5. 


and  so  on  to  the 


CHAPTER    XVIII 


THE   TICKS 


Class  Arachnida,  Order  Acarina,  Superfamily  Ixodoidea 

Characteristics  of  Arachnida.  — •  The  general  characteristics  of  the 
class  Arachnida  have  already  been  pointed  out  in  an  earlier  chapter, 
but  it  is  in  place  to  refer  to  these  once  more.  In  the  arachnids  the 
adults  always  have  four  pairs  of  legs  (the  larvae  are  commonly  hexapod) , 
wings  are  absent  as  are  antennae  and  compound  eyes.  Simple  eyes 
may  be  present  or  absent ;  when  present  they  are  often  more  than  two 
in  number.  The  mouth  parts  usually  consist  of  a  pair  of  piercing 
chelicerse.  The  respiratory  organ  in  some  arachnids,  for  example 
spiders,  is  called  a  "  lung  book  "  ;  in  many  species  however,  particularly 
ticks,  there  is  present  a  well-defined  tracheal  breathing  system.  The 
body  is  commonly  divided  into  two  parts,  —  cephalothorax  and  ab- 
domen, the  former  bearing  the  walking  appendages.  In  many  species, 
for  example,  the  ticks  and  mites,  the  regions 
of  the  body  are  fused.  The  sexes  are  distinct 
and  there  is  often  marked  sexual  dimorphism. 

Order  Acarina.  —  To  the  order  Acarina  be- 
long the  ticks  and  mites.  The  cephalothorax 
and  abdomen  are  fused,  the  larvae  have  only 
three  pairs  of  legs ;  the  eyes  in  the  parasitic 
forms  are  either  very  small  or  entirely  wanting. 
The  members  of  this  group  are  never  large, 
some  ticks  may  be  15-16  mm.  in  length,  while 
many  of  the  mites  are  barely  visible  to  the 
naked  eye. 

The  Ticks.  —  The  ticks  are  acari  varying  in 
size  from  1  mm.  in  the  seed  tick  or  larval  stage 
to  about  15  mm.  in  the  fully  engorged  mature 
female  of  several  species.     They  are  found  in 
all  parts  of  the  world  and  are  commonly  re- 
garded as  pests  of  domesticated  animals  and  frequently  attack  man. 
The  ticks  belong  to  the  superfamily  Ixodoidea.     They  are  blood- 
sucking arachnid  parasites,  body  covered  with  a  leathery,  more  or  less 
glossy  cuticle,  the  head  or  capitulum  consisting  of  characteristic  pro- 

296 


Fig.  187.  —  Capitulum  of 
a  tick  (larval  Argas),  ven- 
tral aspect,  showing  (1) 
basis  capituli ;  (2)  palpi ; 
(3)  hypostome ;  (4)  che- 
licerse  ;  (5)  hood  or  sheath 
of  chelicerse ;  (6)  denticles 
of  chelicerse.  (Drawing 
by  W.  L.  Chandler.) 


THE  TICKS  297 

trusible  chelicerse  and  a  serrate  hypostome  (Fig.  187).  The  females 
are  capable  of  very  great  distention,  having  the  appearance  of  a  seed 
rather  than  that  of  an  insect. 

Life  History.  —  The  Hfe  histories  of  ticks  vary  considerably  for  the 
several  species,  hence  it  is  quite  impossible  to  generalize,  except  that 
it  may  be  said  that  all  species  of  ticks,  with  very  few  exceptions,  pass 
through  four  stages,  • —  egg,  seed  tick,  nymph  and  adult  and  that  from  six 
weeks  to  over  six  months  are  required  to  pass  through  these  four  stages. 
Eggs  are  deposited  by  the  fully  engorged  females,  the  number  varying 
from  100  in  some  species  to  5000  and  over  in  others.  The  newly  hatched 
larvfe,  known  as  seed  ticks,  are  hexapod  (six-legged)  and  remain  in  this 
condition  until  the  first  molt.  The  nymph  emerges  from  the  first 
molt  with  its  fourth  pair  of  legs  present,  and  remains  in  this  stage 
until  the  second  molt,  after  which  the  adult  tick  emerges ;  often  a  third 
or  even  a  fourth  molt  or  more  takes  place  before  the  adult  stage  is 
reached.  Copulation  takes  place  after  the  last  molt,  when  the  females 
engorge  and  then  deposit  eggs.  In  the  majority  of  species,  the  ticks 
drop  off  the  host  animal  to  molt,  but  in  several  species,  notably  the 
Texas  cattle  fever  tick  {Margaropus  annulatus),  the  molting  takes 
place  on  the  host.  Eggs  are  invariably  deposited  on  the  ground  by 
the  fully  engorged  females.  There  may  be  two  or  possibly  three  genera- 
tions of  ticks  in  one  year  under  very  favorable  climatic  conditions  in 
such  species  as  molt  on  the  host. 

The  seed  ticks  emerging  from  the  eggs  on  the  ground  commonly 
climb  up  grasses  and  other  low  vegetation,  thus  coming  in  easy  reach 
of  grazing  or  passing  animals.     The  nymphs  employ  the  same  method. 

Tick  Mouth  Parts.  —  The  capitulum  or  head  bears  the  mouth  parts 
and  accessory  external  structures  (Fig.  187).  The  basal  portion  is 
known  as  the  basis  capitidi,  from  which  projects  forward  and  dorsally  a 
pair  of  protrusible  chelicerce.  The  distal  portions  (digits)  of  the  chelicerse 
are  divergent  and  provided  with  recurved  teeth.  Projecting  forward 
and  situated  ventrally  and  median  on  the  basis  capitidi  is  the  hypostome 
bearing  many  recurved  teeth.  Laterally  are  located  the  palpi  (one  pair), 
consisting  of  four  articles,  of  which  two  or  more  may  be  fused,  —  com- 
monly only  three  are  visible. 

Feeding  Habits.  —  When  sucking  blood  both  the  hypostome  and 
the  chelicerse  are  inserted  into  the  tissue  of  the  host.  Because  of  the 
recurved  teeth  the  tick  is  enabled  to  hold  so  fast  to  the  host  that  it  is 
difficult  to  remove  it  without  tearing  the  capitulum  from  the  body  of 
the  tick.  The  tick  itself,  however,  withdraws  its  mouth  parts  quickly 
and  apparently  with  little  effort  by  slipping  the  hoodlike  portions  of  the 
capitulum  over  the  relaxed  mouth  parts  and  by  means  of  a  quick  jerk 
drops  off  and  escapes. 

The  length  of  time  that  a  tick  remains  attached  in  the  act  of  feeding 
depends  entirely  on  the  species  and  the  stage  of  development.  The 
seed  ticks  commonly  feed  for  a  number  of  days  ;  the  nymphs  and  adults 


298        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

differ  greatly  in  this  respect,  —  thus  the  common  poultry  tick  (Argas 
persicus)  feeds  nightly  and  intermittently,  while  the  nymphs  and  adults 
of  the  cattle  tick  (Margaropus  annulatus)  feed  from  six  to  eight 
days  before  becoming  engorged.  Other  species  of  ticks,  notably  the 
Pajaroello  (Ornithodorus  coriaceus) ,  engorge  themselves  fully  in  from 
fifteen  to  twenty-five  minutes. 

Longevity.— The  longevity  and  hardiness  of  ticks  is  something 
truly  remarkable,  a  matter  not  to  be  overlooked  in  control  measures, 
particularly  pasture  rotation  in  which  starvation  is  the  principal  factor. 
Furthermore,  fluids  which  destroy  the  life  of  most  insects  in  a  few 
minutes  act  very  slowly  on  these  arachnids,  for  example,  immersion  in 
70  per  cent  alcohol  will  not  kill  the  ticks  for  hours  and  xylol  is  resisted 
for  about  half  an  hour.  The  writer  has  found  the  poultry  tick  Argas 
persicus  particularly  resistant. 

Unfed  larval  ticks  of  the  above  species  remain  alive  quite  readily 
for  a  month  and  would  probably  survive  longer  if  kept  in  a  moist  cham- 
ber. Nymphs  survive  a  longer  time  and  the  adults  even  longer  than 
the  nymphs.  Nuttall^  cites  cases  in  which  nymphs  of  this  species 
survived  two  months,  and  adults  (unfed)  "a  little  over  two  years."  Gray- 
bilF  reports  considerable  variation  in  the  longevity  of  the  Texas  fever 
tick,  depending  on  the  season  of  the  year;  unfed  larvse  survived 
from  7  to  85  days  (aver.  38.6)  for  July,  and  30  to  234  days  (aver.  167.4) 
for  October.  Nuttall  ^  cites  cases  in  which  the  larvae  of  Ixodes  riciiius 
survived  19  months,  unfed  nymphs  18  months  and  unfed  adults  15  to 
27  months. 

Major  Divisions  (classification) .  —  All  ticks  (superf amily  Ixodoidea) 
are  commonly  divided  into  two  families,  viz. :  Argasidse  (also  referred 
to  as  subfamily  Argasinse)  and  Ixodidse  (also  referred  to  as  subfamily 
Ixodinse).  The  presence  of  a  scutum  (or  shield)  located  dorsally  imme- 
diately posterior  to  the  capitulum  in  the  Ixodidae  is  the  most  striking 
differential  character.     This  character  is  absent  in  the  Argasidse. 

The  following  table,  on  page  300,  adapted  after  Nuttall  (1908, 
loc.  cit.),  will  be  found  useful  in  separating  the  two  families.  (See 
also  Fig.  188.) 

1  Nuttall,  G.  H.  F.,  and  Warburton,  Cecil,  1908.  Ticks,  a  monograph  of 
the  Ixodoidea,  Part  I,  Argasidse.  pp.  x  +  104  +  35.  Cambridge  (England), 
Univ.  Press. 

2  Gray  bill,  H.  W.,  1911.  Studies  on  the  biology  of  the  Texas  fever  tick. 
U.  S.  Dep.  of  Agric,  Bur.  Animal  Ind.  Bull.  130. 

'NuttaU,  G.  H.  F.,  and  Warburton,  Cecil,  1911.  Ticks,  a  monograph  of 
the  Ixodoidea.  Part  II,  Ixodidse.  pp.  xix  +  105  +  348.  Cambridge, 
(England),  Univ.  Press. 


THE  TICKS 


299 


300        MEDICAL  AND  VETERINARY  ENTOMOLOGY 


TABLE  XXI 

Differences  by  Which  the  Two  Families   of  the   Ixodoidea  may 
BE   Separated.     (Adapted  after  Nuttall) 


Sexual  dimor'phism 
Capituluni 

Base 

Palpi 


Body 


Scutum 

Festoons 

Eyes  (when  present) 


Legs 


Coxae 
Tarsi 
Pulvilli 


Argasid^ 


Slight 
Ventral 

No  porose  areas 
Leg-like,  with    subequal 
articles 

Absent 
Absent 

Lateral    on     supracoxal 
folds 

Unarmed 

Without  ventral  spurs 

Absent  or  rudimentary 


IXODID^ 


Marked 
Anterior 

Porose  areas  in  9 
Relatively  rigid,  of  very 
varied  form 

Present 

Generally  present 
Dorsal   on   the   sides   of 
the  scutum 

Generally     armed     with 

spurs 
Generally  armed  with  1 

or  2  ventral  spurs 
Always  present 


The  Ixodine  Ticks 
The  Texas  Cattle  Fever   Tick 


The  Texas  Cattle  Fever  Tick  {Margaropus  annulatus  Say  =  Boophihts 
bovis  Riley)  is  economically  considered  the  most  important  species  of 
the  family  Ixodidse  (Fig.  189).  It  is  restricted  to  North  America,  where 
it  occurs  south  of  the  Mason  and  Dixon  line.     It  is  typically  a  cattle 

tick,  although  it  occurs  at  times  in 
smaller  numbers  on  deer,  sheep 
and  other  animals. 

Fully  engorged  females  range 
in  length  from  10  to  12  mm.,  while 
the  males  range  from  3  to  4  mm. 
The  body  of  the  female  is  about 
equally  rounded  both  posteriorly 
and  anteriorly  with  slight  median 
incurving.  The  anterior  pair  of 
legs  is  set  well  out  on  the  shoul- 
ders away  from  the  capitulum  (in 
Dermacentor  close  to  the  capit- 
ulum).     The  palpi  are  very  short 


Fig.  189.  —  The  Texas  fever  tick,  Marga- 
ropus annulatus ;  female  (left)  and  male 
(right).      X  3.5. 


THE  TICKS  301 

and  stalky,  so  that  the  entire  capitulum  or  head  is  inconspicuous. 
The  relatively  small  (1+  mm.  long)  scutum  or  shield  is  solid  chest- 
nut brown  in  color.  This  is  commonly  the  only  species  of  tick 
in  some  localities  with  a  chestnut-brown  scutum.  Two  other  species 
of  ticks  with  a  chestnut-colored  scutum  occur  occasionally  with  the 
Texas  fever  tick,  namely  the  "  Lone  Star  Tick,"  Amhlyomma  amer- 
icanum,  which  has,  however,  a  distinct  silver  white  circular  spot 
at  the  posterior  end  of  the  scutum,  and  Ixodes  ricinus  and  its  varieties, 
e.g.  Ixodes  californicus,  in  which  the  capitulum  is  long,  and  the  anterior 
pair  of  legs  are  attached  close  to  it.  Other  technical  diagnostic  details 
are  of  course  present  in  the  latter  two  species. 

The  stigmal  plates  of  M.  annulatus  are  nearly  circular ;  the  porose 
areas  are  elliptical  and  far  apart. 

Economic  Importance.  —  It  has  been  estimated  ^  that  the  annual 
losses  to  the  South  (U.S.)  occasioned  by  the  "cattle  tick"  directly  and 
indirectly  prior  to  1906  amounted  to  $130,500,000.  These  losses  are 
summed  up  as  follows  : 

"1.  Death,  from  Texas  fever,  of  pure  bred  cattle  imported  from  the 
North  for  breeding  purposes. 

"2.  Death,  from  Texas  fever,  when  cattle  reared  in  isolated  tick- 
free  areas  are  unintentionally  or  accidentally  placed  with  ticky  cattle, 
or  on  tick-infested  areas. 

"3.  Death  of  native  cattle  from  excessive  parasitism  and  fever,  ■ 
occasioned  by  the  ticks. 

"  4.  Universal  loss  of  weight  by  all  tick-infested  cattle,  and  their 
failure  to  gain  flesh  at  a  rate  great  enough  to  make  beef  production 
profitable. 

"  5.  The  lower  price  which  "  Southern  "  cattle  bring  upon  the 
market,  regardless  of  how  perfect  their  condition  may  be. 

"  6.   Sterility  induced  in  high-grade  cattle  by  tick  infestation. 

"7.  The  expense  of  maintaining  the  Federal  quarantine  for  the 
protection  of  the  North  against  invasion  by  the  tick,  and  the  added 
expense  of  maintaining  quarantine  pens  for  Southern  cattle  shipped 
north  for  slaughter. 

"8.  The  discouraging  eflFect  on  the  breeding  of  pure  bred  cattle  in 
the  South  by  reason  of  Southern  breeders  not  being  allowed  to  exhibit 
in  Northern  show  rings. 

"  9.  By  no  means  least,  the  potential  loss  in  fertility  of  Southern 
farm  lands  due  to  a  one-crop  system  which,  with  the  tick  eradicated, 
would  quickly  give  way  to  a  diversified  agriculture  which  would  con- 
serve and  increase  the  fertility  of  our  soils." 

Life  History  of  Texas  Fever  Tick.  —  Most  careful  observations  on 
the  biology  of  the  Texas  fever  tick  have  been  made  by  the  Bureau  of 
Animal  Industry  of  the  U.  S.  Department  of  Agriculture  and  the  fol- 

1  State  Crop  Post  Commission  of  Louisiana,  1906.  Circ.  No.  10,  "The 
cattle  tick." 


302        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

lowing  data  is  adapted  after  Graybill  {1911,  loc.  cit.).  The  maximum 
number  of  eggs  deposited  by  a  female  tick  according  to  this  author  was 
5105,  minimum  357,  with  an  average  ranging  from  1811  to  4089. 
The  period  of  oviposition,  time  during  which  female  deposits  eggs, 
ranged  from  an  average  of  8.3  days  for  June  (1907)  to  127.5  days  for 
November.  The  maximum  period  was  152  days  and  the  minimum  3 
days,  depending  on  temperature  mainly.  The  incubation  period,  also 
dependent  on  temperature,  ranged  from  19  days  in  summer  to  180  days 
in  the  early  autumn,  with  the  average  of  43.6  days  for  April,  26.3  days 
for  May,  24.5  days  for  June,  20.5  days  for  July,  21.2  days  for  August 
and  35.9  days  for  September.  The  hatching  period  depends  on  the 
time  when  the  eggs  are  laid,  the  eggs  first  deposited  ordinarily  hatching 
first.  The  average  period  ranged  from  10.6  days  for  July  to  36  days 
for  October,  with  a  maximum  period  of  49  days  and  a  minimum  of  4 
days.  The  time  during  which  the  seed  ticks  remain  alive,  i.e.  longevity 
of  the  newly  hatched  ticks,  again  varies  considerably,  depending  on  tem- 


FiG.   190.  —  Eggs  (left),  larva  (right),  of   the   Texas   fever  tick,    Margaropus  annulatus. 

X50. 


perature;  the  longevity  for  April  was  found  to  be  65.1  days.  May  62.3 
days,  June  65.1  days,  July  38.6,  August  84.9  days,  October  167.4  days. 
The  total  average  time  for  the  non-parasitic  period  ranged  from  86.9 
days  for  June  to  279.6  for  October. 

The  three  stages  (Fig.  190)  considered  in  the  parasitic  period  of  the 
ticks  are  larval  (seed  tick),  nymphal  and  adult.  As  Graybill  has  well 
said,  "  The  duration  of  each  of  these  stages  and  the  duration  of  a  single 
infestation  upon  cattle  during  different  portions  of  the  year  are  of  great 
practical  importance.  Upon  the  duration  of  an  infestation  depends 
the  time  animals  must  be  kept  on  the  tick-free  fields  in  order  to  become 
free  from  ticks."  This  author  has  found  that  after  the  seed  tick  has 
attached  itself  to  the  host  the  minimum  larval  period  ranges  from  five 
to  seven  days,  the  minimum  nymphal  period  of  females  from  nine  to 
thirty  days,  and  the   adult   from  five    to   thirty-three    days,  with   a 


THE  TICKS 


303 


total  period  of  infestation,  including  the  time  for  molting  twice,  which 
is  accomplished  on  the  host,  at  from  thirty  to  sixty-six  days. 

The  more  striking  differences  between  the  life  histories  and  a  com- 
parison of  the  life  cycle  of  the  Texas  fever  tick  and  the  common  dog 
tick  {Dermacentor  electus)  are  shown  in  the  following  two  tables  (Tables 
XXII  and  XXIII),  adapted  after  Cotton:^ 

TABLE   XXII 

Comparison  op  the    Length  of  the   Life  Cycle  of  the   Dog  Tick  and 
OF  THE  North  American  Fever  Tick  in  Summer 

(After  Cotton,  loc.  ciL,  1908) 


Dog  Tick 
{Dermacentor  sp.) 


I.  Adult  tick  becomes  engorged  on 
host  animal  and  drops  to 
ground 


North  American  Fever  Tick 
{Margaropus  anmUalua) 


II.    Engorged  tick  begins  egg  laying 
(3000  ±  eggs)  after  3-5  days 


Adult  tick  becomes  engorged  on  host 
animal  and  drops  to  ground 


Adult  tick  begins  egg  laying  (3000  ± 
eggs)  after  3-5  days 


III.   Seed  ticks  hatch  from  eggs  in 
about  30  days 


Seed  ticks  hatch  from  eggs  in  about 
30  days 


IV.  Seed  ticks  bunch  on  grass  and 
await  coming  of  host  animal, 
from  one  day  to  several  weeks 


Seed  ticks  bunch  on  grass  and  await 
coming  of  host  anin  al  from  one  day 
to  several  weeks 


V.  After  feeding  7-12  days  seed 
ticks  drop  to  ground  and 
molt 


VI.  Ticks  crawl  up  on  grass  and 
await  coming  of  second  host 
animal  from  one  day  to 
several  weeks 


After  feeding    7-12  days    seed    ticks 
molt  on  host  animal 


VII.  Ticks  get  on  second  host  animal 
and  feed  5-10  days,  then  drop 
to  ground  and  molt  second 
time 


VIII.   Ticks   crawl   up  on  grass  and 

await   coming  of  third   host 

animal    from  one    day    to 
several  weeks 


Ticks  feed   5-10  days,  then  molt  on 
host  animal  and  mate 


IX.  Adult  ticks  mate  and  feed  5-8 
days,  then  drop  to  the  ground 
and  lay  eggs 


Adult  ticks  feed  4-14  days  then  drop 
to  the  ground  and  lay  eggs 


1  Cotton,  E.G.,  1908. 
Tennessee  Bull.  81. 


Tick  eradication.     Agr.  Exp.  Sta.  of  the  Univ.  of 


304 


MEDICAL  AND  VETERINARY  ENTOMOLOGY 


TABLE   XXIII 

Showing  Prominent  Differences   between  the  Life   Histories  of  the 
Dog  Tick  and  the  North  American  Fever  Tick 

(After  Cotton,  loc.  cit.,  1908) 


Dog  Tick 
(Dermacentor  sp.) 

North  American  Fever  Tick 
{Margaropus  annulatus) 

Leaves  host  animal  for  each  molt 

Never  voluntarily  leaves  host  animal 
from  attachment  as  a  seed  tick  until 
fully  mature 

Requires  three  separate  host  animals  or 
may  get  on  same  host  three  times 

Requires  but  one  host  animal  to  reach 
maturity  and  gets  on  this  one 
animal  but  once 

Can  develop  on  a  large  number  of  dif- 
ferent kinds  of  animals 

Must  find  cow,  horse,  mule  (deer  or 
sheep)  as  a  host  animal  or  perish 

Does  not  transmit  Texas  fever 

Only  natural  means  of  transmission  of 
Texas  fever  from  one  cow  to  another 

Usually  requires  a  whole  year  to  com- 
plete its  life  cycle,  from  egg  through 
seed  tick,  nymph,  and  adult,  to  egg 
again 

Is  able  to  complete  its  life  cycle  in 
about  60  days,  thus  allowing  for 
three  generations  in  one  year,  pro- 
vided hosts  are  available 

Because  of  the  habit  of  dropping  to  the 
ground  at  each   molt  the   parasitic 
and  non-parasitic  periods  intermingle 
and  therefore  the  life  cycle  cannot  be 
divided  into  two  distinct  parts 

Life  cycle  is  divided  into  two  separate 
and  distinct  parts ;  parasitic,  passed 
on  the  host  animal,  and  non-parasitic, 
passed  off  the  host  animal 

The  habit  of  dropping  to  the  ground  for 
each    molt    materiallj^  reduces    the 
chances   of  the   seed   ticks   of  this 
species  reaching  maturity 

The  habit  of  remaining  on  the  host 
animal  until  maturity  renders  it 
almost  certain  that  every  seed  tick 
of  this  species  finding  attachment 
wiU  reproduce  itself 

Since  the  species  has  but  one  generation 
per  year  the  progeny  of  one  adult  tick 
will  produce  1,050,000  eggs  in  a  single 
season 

Since  this  species  has  three  generations 
per  year  the  progeny  of  one  adult  tick 
will  produce  5,82*5,036,452,578,000 
eggs  in  a  single  season 

THE   TICKS  305 

Piroplasmosis  applies  to  a  group  of  diseases  traceable  to  the  Pro- 
tozooii  genus  Babesia  (Piroplasma),  and  related  genera  such  as  Theileria, 
Nuttalia,  etc.,  belonging  to  the  subphylum  Sporozoa,  class  Telosporida, 
subclass  Hsemosporida,  order  Xenosporida.  The  genus  Babesia  com- 
prises pear-shaped  (varying  somewhat  to  oval),  red  blood-cell  inhabiting 
parasites  (Fig.  191).  Unlike  the  Plasmodia  there  is  little  or  no  pigment, 
and  multiplication  is  by  division  in  twos.  Ticks  are  the  usual  carriers  in 
which  there  is  hereditary  transmission  from  the  female  tick  to  the  egg, 
and  thus  to  the  larva  and  nymph  which  act  as  the  infecting  agents. 
The  most  important  example  of  Piroplasmosis  is  Texas  cattle  fever. 

Texas  Cattle  Fever.  —  Babesia  (Piroplasma)  bigemina,  Smith  and 
Kilbourne  is  the  causative  organism  of  Texas  cattle  fever,  also  vari- 
ously known  as  red  water,  splenic  fever,  tick  fever,  etc.  The  dis- 
ease is  widely  distributed,  being  endemic  in  southern  Europe,  Central 
and  South  America,  parts  of  Africa,  Mexico,  the  Philippines,  and  the 

southern  United  States  where  it  has  been 
known  for  more  than  a  century,  having 
been  introduced  into  this  country  probably 
from  Europe. 

The  name  Texas  fever  became  attached 
to  the  disease  because  of  the  large  herds  of 
cattle  which  were  driven  northward  from 
Texas  and  gave  a  certain  disease  in  some 
mysterious  manner  to  Northern  cattle  that 
crossed  the  trail  of  the  Southern  cattle.  The 
Fig.  191.  —^B^besia  bigemina  Srst  account  of  the  disease  was  given  by 
(Piroplasma  bovis),  showing    James  Mcasc  in  1814  before  the  Philadelphia 

three  stages  in  intracorpus-      o      •    ,       p       -n  ,•         a       •       i,  x      -l7^-r^ 

cuiar  development.    X  2000.    Socicty  tor  Promoting  Agriculture.     In  18/9, 

Salmon  began  an  investigation  of  the  dis- 
ease; and  in  1889,  Theobald  Smith  made  his  epoch-making  discovery 
of  the  intracorpuscular  protozoan  parasite  inhabiting  the  blood  of  the 
diseased  cattle.  Immediately  thereupon  followed  the  experiments  of 
Kilbourne,  on  suggestion  of  Salmon,  which  proved  the  disease  to  be 
tick-borne,  a  suspicion  held  as  early  as  1869  according  to  Smith  and 
Kilbourne.  Until  that  time  (1889)  infection  was  variously  attributed 
to  saliva,  urine  or  feces. 

The  disease  may  assume  either  an  acute  or  chronic  form,  the  acute 
occurring  during  the  summer  months  and  the  chronic  during  the  autumn 
and  early  winter.  The  symptoms  ^  of  the  acute  form  are  as  follows: 
The  temperature  often  registers  106°  to  108°  F.  within  forty-eight  hours 
after  the  first  symptoms  are  noticed.  The  sick  animal  leaves  the  herd, 
stands  with  arched  back  and  ears  drooping,  the  muzzle  dry,  appetite 
lost  and  rumination  stopped.  There  is  constipation  during  the  first 
stage  of  the  disease,  which  may  give  way  to  diarrhea  later.     The  manure 

1  Adapted  largely  after  the  description  of  L.  L.  Lewis,  1908.  Texas  fever. 
Okla.  Agr.  Exp.  Sta.  BuU.  No.  81. 


306        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

is  frequently  stained  with  bile  and  may  be  tinged  with  bloody  mucus ; 
the  urine  is  often  very  dark  red  or  coffee-colored.  The  blood  becomes 
thin  and  watery,  so  that  by  making  an  incision  into  the  tip  of  the  ear 
and  allowing  the  blood  to  flow  over  the  hand  it  does  not  stick  to  the 
hand  as  does  the  blood  from  a  healthy  animal. 

Vast  numbers  of  red  blood  corpuscles  are  destroyed  by  the  para- 
sites, which  accounts  in  a  measure  for  the  reddish  color  of  the  urine 
through  the  elimination  of  hsemaglobin  by  the  kidneys ;  and  it  is  believed 
that  the  excessive  work  that  the  liver  has  to  perform  in  attempting  to 
transform  the  excess  of  destroyed  corpuscles  into  bile,  causes  this  organ 
to  become  deranged  in  function,  and  eventually  a  complete  stagnation 
may  result  with  fatal  termination.  Mortality  ranges  from  fifty  to 
seventy-five  per  cent. 

The  chronic  form  of  the  disease  is  often  hardly  noticeable.  The 
following  comment  by  Lewis  {loc.  cit.)  is  significant :  "  This  is  the  type 
of  fever  usually  seen  among  Southern  cattle.  Death  does  not  occur  as 
a  rule,  but  the  loss  in  growth  and  general  condition  is  such  as  to  make 
this  type  of  disease  very  important.  It  is  this  loss  in  growth  and  con- 
dition rather  than  an  actual  numerical  loss  by  death  that  constitutes 
the  great  damage  suffered  by  the  stock  industry  of  the  South." 

Babesia  bigemina  (Piroplasma  (bovis)  bigeminum),  the  causa- 
tive protozoan  parasite  of  Texas  cattle  fever,  was  discovered  by 
Theobald  Smith  in  1889  and  was  called  Pyrosoma  bigeminum.  The 
parasite  (Fig.  191)  is  described  by  Smith  and  Kilbourne  ^  as  follows: 
"  When  blood  is  drawn  from  the  skin  during  the  fever,  and  examined 
at  once  with  high  powers  (500  to  1000  diameters  .  .  .)  certain  cor- 
puscles will  be  found  containing  two  pale  bodies  of  a  pyriform  outline. 
One  end  of  each  body  is  round  and  the  body  tapers  gradually  to  a  point 
at  the  other.  They  vary  somewhat  in  size  in  different  cases,  but  the 
two  bodies  in  the  same  corpuscle  are  as  a  rule  of  the  same  size.  They 
are  from  2  to  4  ft  in  length  and  1.5  to  2  /a  in  width  at  the  widest  por- 
tion. Their  tapering  ends  are  directed  toward  each  other  and  usually 
close  together ;  their  rounded  broad  ends  may  occupy  various  positions 
with  reference  to  each  other.  They  may  be  seen  together  with  the 
axes  of  the  bodies  nearly  parallel  or  they  may  be  far  apart,  the  axes 
forming  a  straight  line.  The  bodies  themselves  have  a  homogeneous, 
pale  appearance,  contrasting  markedly  with  the  inclosing  red  corpuscles 
from  which  they  are  sharply  outlined.  There  is  no  differentiation  into 
peripheral  and  central  zone,  no  granular  appearance  of  the  body.  .  .  . 
When  exposed  to  a  temperature  of  35°  C.  to  42°  C.  on  the  warm  stage 
some  of  these  bodies,  by  no  means  all,  exhibited  changes  of  outline. 
These  may  go  on  continuously  in  some  bodies,  in  others  quite  slowly. 
The  motion  most  frequently  exhibited  consists  not  so  much  of  a  thrust- 

1  Smith,  T.,  and  Kilbourne,  F.  L.,  1893.  Investigations  into  the  nature, 
causation  and  prevention  of  Texas  or  Southern  cattle  fever.  U.  S.  Dept.  of 
Agric,  Bur.  Animal  Ind.  Bull.  No.  1,  301  pp. 


THE   TICKS  307 

ing  out  and  withdrawing  of  pseudopodia  as  of  a  continual  recasting  of 
the  general  outline  of  the  body  as  we  find  it,  for  example,  in  the  leuco- 
cytes of  mammalian  blood.  .  .  .  The  number  of  infected  corpuscles 
circulating  in  the  blood  during  the  high  fever  is  usually  quite  small  .  .  . 
from  half  to  one  per  cent  is  near  the  truth  in  most  cases.  .  .  .  Toward 
the  fatal  termination,  there  may  be  from  5  to  10  per  cent  of  the  cor- 
puscles with  the  pyriform  parasites  present." 

In  1888  an  "  investigation  into  the  nature,  causation  and  preven- 
tion "  of  the  disease  was  undertaken  by  the  United  States  Department 
of  Agriculture,  Bureau  of  Animal  Industry,  under  the  direction  of  Dr. 
D.  E.  Salmon.  The  work  was  done  by  Dr.  Theobald  Smith  and  Dr. 
F.  L.  Kilbourne  and  marks  a  most  important  epoch  in  our  knowledge 
of  protozoan  diseases  and  in  preventive  medicine. 

During  a  period  of  about  four  years  of  nearly  continuous  investi- 
gation, the  problem  was  exhaustively  studied  in  both  the  field  and  in 
the  laboratory.  The  field  experiments  were  carried  along  three  different 
lines,  viz.:  "  (1)  Ticks  were  carefully  picked  from  Southern  animals 
so  that  none  could  mature  and  infect  the  ground.  The  object  of  this 
group  of  experiments  was  to  find  out  if  the  disease  could  be  conveyed 
from  Southern  to  Northern  stock  on  the  same  inclosure  without  the 
intervention  of  ticks.  (2)  Fields  were  infected  by  matured  ticks  and 
susceptible  cattle  placed  on  them  to  determine  whether  Texas  fever 
could  be  produced  without  the  presence  of  Southern  cattle.  (3)  Sus- 
ceptible Northern  cattle  were  infected  by  placing  on  them  young  ticks 
hatched  artificially,  i.e.  in  closed  dishes  in  the  laboratory "  (Smith 
and  Kilbourne,  1893,  loc.  cit.). 

Healthy  native  cattle  (Washington,  D.C.)  were  exposed  to  sick 
native  cattle  free  from  ticks  for  months  without  contracting  the  dis- 
ease, proving  that  the  excretions  had  nothing  to  do  with  the  trans- 
mission of  the  disease.  In  the  absence  of  ticks,  sick  animals  are  harm- 
less. Again  several  thousand,  mostly  full-grown  ticks,  collected  from 
cattle  in  North  Carolina,  were  scattered  over  the  ground  in  a  field  on 
September  13.  Four  native  cattle  were  placed  in  the  field  Sept.  14; 
of  these  animals  three  contracted  Texas  fever.  This  experiment  was 
repeated  with  five  experimental  animals,  and  a  new-born  calf,  all  of 
which  contracted  the  fever.  A  yearling  heifer  was  placed  in  a  box 
stall  and  a  number  of  young  ticks,  hatched  artificially  in  glass  dishes, 
were  placed  on  the  animal  at  intervals.  The  heifer  contracted  Texas 
fever.  A  repetition  of  this  experiment  on  various  occasions  always 
gave  similar  results.  It  was  definitely  concluded  that  "  Texas  fever  in 
nature  is  transmitted  from  cattle  which  come  from  the  permanently 
infected  territory  to  cattle  outside  this  territory  by  the  cattle  tick 
(Bodphilus  bovis  =  Margaropus  annulatus)  and  that  the  infection 
is  carried  by  the  progeny  of  the  ticks  which  matured  on  infected  cattle, 
alid  is  inoculated  by  them  directly  into  the  blood  of  susceptible  cattle." 
Just  how  the  young  tick  becomes  infected  from  the  parent  tick  is 


308       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

still  a  question,  but  it  seems  reasonable  to  conclude  that  the  protozoon 
migrates  from  the  intestine  of  the  parent,  possibly  in  a  manner  similar 
to  the  development  of  the  malaria  parasite,  eventually  infecting  the 
ovaries  instead  of  the  salivary  glands  as  in  the  mosquito,  and  thus 
the  ova  become  infected  before  ovulation  and  the  newly  emerged 
seed  tick  is  consequently  infective.  The  authors  above  cited  state 
that  the  contents  of  the  bodies  of  ticks  in  various  stages  of  growth 
were  examined  microscopically  with  considerable  care,  but  that  the 
abundant  particles  resulting  from  the  breaking  up  of  the  ingested  blood 
corpuscles  obscured  the  search  so  that  nothing  definite  was  discovered. 
"  The  very  minute  size  of  the  microorganism  renders  its  identification 
well-nigh  impossible,  and  any  attempt  will  be  fraught  with  great  diffi- 
culties." 

Other  tick  carriers  of  the  protozoon  are  Boophilus  australis  Fuller 
and  B.  decolor atus  Koch  within  their  range. 

Controlling  the  Texas  Fever  Tick.  —  This  is  accomplished  in  one  of 
two  general  ways  or  by  a  combination  of  the  two;  namely,  first  by  the 
application  of  tickicides  on  cattle,  and  secondly  by  pasture  rotation 
resulting  in  the  starvation  of  the  seed  ticks  which  have  hatched  from 
the  eggs  deposited  by  dropped  ticks,  the  pasture  being  previously  made 
free  of  ticks  by  a  similar  process.  It  is  not  the  object  of  this  work  to 
give  a  detailed  account  of  the  methods  employed,  hence  the  reader  is 
referred  to  Farmers'  Bulletin  498,  U.  S.  Department  of  Agriculture,  for 
specific  "  Methods  of  exterminating  the  Texas  fever  tick." 

First,  agents  for  the  destruction  of  ticks  on  cattle  are  ordinarily 
either  oil  or  arsenic.  If  the  former  is  used  an  emulsion  is  desirable,  to 
be  applied  with  a  spray  pump  or  in  the  form  of  a  dip.  An  emulsion  of 
crude  petroleum  recommended  by  the  U.  S.  Department  of  Agriculture, 
Bureau  of  Animal  Industry,^  is  prepared  as  follows : 

Hard  soap 1  pound 

Soft  water 1  gal. 

Beaumont  crude  petroleum 4  gal. 

This  formula  is  sufiicient  to  make  five  gallons  of  80  per  cent  stock 
emulsion.  For  use  this  must  be  diluted  with  water  to  a  20  to  25  per 
cent  emulsion,  or  one  part  stock  emulsion  to  three  or  two  and  one-fifth 
parts  of  water. 

To  prepare  the  stock  the  soap  should  be  "  shaved  up  and  placed  in 
a  kettle  or  caldron  containing  the  required  amount  of  water.  The  water 
should  be  brought  to  a  boil  and  stirred  until  the  soap  is  entirely  dis- 
solved. Enough  water  should  be  added  to  make  up  for  the  loss  by 
evaporation  during  this  process.  The  soap  solution  and  the  required 
amount  of  oil  are  then  placed  in  a  barrel  or  some  other  convenient  re- 

1  Graybill,  H.  W.,  1912.  Methods  of  exterminating  the  Texas  fever  tick. 
U.  S.  Dept.  of  Agr.,  Farmer's  Bull.  498. 


THE  TICKS  309 

ceptacle  and  mixed.  The  mixing  may  be  effected  by  the  use  of  a  spray 
pump,  pumping  the  mixture  through  and  through  the  pump  until  the 
emulsion  is  formed.  Only  rain  or  soft  water  should  be  used  for  diluting." 
If  hard  water  is  used,  it  should  be  softened  by  adding  sodium  carbonate 
(sal  soda),  j  pound  to  every  five  gallons  of  water  used.  The  Beaumont 
oil  recommended  has  a  "  specific  gravity  ranging  from  22|°  to  24|° 
Beaume,  containing  1|  to  1|  per  cent  sulphur,  and  40  per  cent  of  the 
bulk  of  which  boils  between  200°  and  300°  C." 

Arsenical  dips  are  now  more  widely  used  than  any  other  kind.  The 
U.  S.  Department  of  Agriculture,  Bureau  of  Animal  Industry  (Graybill, 
1912,  loc.  cit.),  recommends  the  following  formula : 

Sodium  carbonate  (sal  soda) 24  pounds 

Arsenic  trioxid  (white  arsenic) 8  pounds 

Pine  tar 1  gal. 

Water  sufficient  to  make  500  gallons. 

The  following  directions  are  given  by  the  Bureau  of  Animal  Indus- 
try for  the  preparation  and  use  of  the  above  arsenical  dip : 

"In  preparing  the  dip  a  large  caldron  or  galvanized  tank  is  required  for 
heating  the  water  in  which  to  dissolve  the  chemicals.  Twenty-five  gallons  of 
water  should  be  placed  in  the  caldron  or  tank  and  brought  to  a  boil.  The 
amount  of  sodium  carbonate  indicated  in  the  fonnula  is  then  added  and  dis- 
solved by  stirring.  When  this  is  accomplished,  the  required  amount  of  arsenic 
is  added  and  dissolved  in  a  similar  manner.  The  fire  is  then  drawn,  and  the 
solution  permitted  to  cool  to  140°  F.,  or  this  process  may  be  hastened  by  the 
addition  of  cold  water.  The  pine  tar  is  then  added  slowly  in  a  thin  stream 
and  thoroughly  mixed  with  the  solution  by  constant  stirring.  This  solution 
should  be  diluted  at  once  to  500  gallons. 

"The  caldron  or  tank  and  utensils  used  in  preparing  the  dip  should  be  kept 
free  from  grease  or  oil,  as  small  quantities  of  these  may  envelop  particles  of 
arsenic  and  prevent  or  hinder  the  solution  of  the  arsenic.  It  should  also  be 
borne  in  mind  that  when  hard  water  is  used  in  the  preparation  of  the  dip  the 
dissolving  of  the  sodium  carbonate  (sal  soda)  in  the  boiling  water  results  in  the 
formation  of  a  fine  white  or  gray  insoluble  powder  or  precipitate  of  lime  salts 
which  may  be  taken  for  undissolved  arsenic,  and  thus  lead  to  the  belief  that  all 
of  the  arsenic  has  not  gone  into  solution, 

"The  arsenical  solution  when  prepared  according  to  the  above  method  should 
be  diluted  as  soon  as  the  pine  tar  has  been  added,  in  order  that  the  tar  may  be- 
come properly  emulsified.  In  the  concentrated  solution  the  tar  tends  to  separate 
out,  especially  when  the  solution  becomes  cold,  and  collect  in  a  laj^er  at  the 
bottom  of  the  container.  Even  when  the  plan  of  immediately  diluting  the  solu- 
tion is  followed  a  satisfactory  emulsion  is  not  always  obtained,  and  some  of  the 
tar  may  separate  and  go  to  the  bottom  of  the  vat. 

"If,  however,  the  acids  present  in  the  tar  are  neutralized  by  the  use  of  con- 
centrated lye,  a  good  emulsion  of  the  tar  in  the  diluted  dip  may  be  obtained.^ 
The  neutralization  is  effected  b5''  dissolving  1  pound  of  concentrated  lye  in  a 
quart  of  water  for  every  gallon  of  tar  to  be  used  and  adding  this  solution  to  the 
tar,  stirring  thoroughly.  When  the  acids  of  the  tar  have  been  properly  neutral- 
ized the  resulting  mixture  should  be  a  bright,  thick  fluid  of  a  dark  brown  color. 

^  This  method  of  emulsifying  the  tar  has  been  suggested  by  the  Bioehemie 
Division  of  the  Bureau  of  Animal  Industry. 


310        MEDICAL  AND   VETERINARY   ENTOMOLOGY 

Whether  the  acids  have  been  neutraUzed  or  not  may  be  determined  by  taking  a 
small  quantity  of  the  tar  on  the  blade  of  a  pocket  knife  or  on  a  sliver  of  wood 
and  stirring  it  in  a  glass  of  water.  If  the  acids  have  been  neutralized,  the  tar 
will  mix  uniformly  with  the  water ;  whereas,  if  they  have  not  been  neutralized, 
the  tar  will  float  about  in  the  water  in  the  form  of  various-sized  globules  that 
will  settle  to  the  bottom  when  the  agitation  of  the  water  ceases.  For  all  ordinary 
grades  of  tar  one  pound  of  lye  to  the  gallon  will  be  ample  to  effect  neutralization, 
but  if  on  testing  it  is  found  that  this  amount  has  not  been  sufficient,  it  will  be 
necessary  to  add  more  lye  solution,  about  a  pint  at  a  time  for  each  gallon,  until 
the  test  shows  that  the  acids  have  been  neutralized.  The  neutralized  tar  should 
be  added  to  the  diluted  arsenical  dip  and  not  to  the  concentrated  solution,  with 
which  it  will  not  mix  satisfactorily.  When  the  neutralized  tar  is  used  the  vat 
should  be  filled  with  diluted  arsenic-soda  solution  prepared  in  the  usual  way. 
The  required  amount  of  neutralized  tar,  diluted  with  two  to  three  times  its 
volume  of  water,  should  then  be  added  to  tlie  solution  in  the  vat  and  thoroughly 
mixed  with  the  same  by  stirring. 

"Before  filling  a  vat  the  capacity,  at  the  depth  to  which  it  is  necessary  to 
fill  it  for  dipping,  if  not  known,  should  be  calculated,  and  for  future  convenience 
the  water  line  should  be  plainly  marked  at  some  point  on  the  wall  of  the  vat. 
Unless  this  is  done  it  will  be  necessary  either  to  calculate  the  amount  of  water 
in  the  vat  each  time  it  is  filled  or  measure  it  as  it  is  placed  in  the  vat,  both  of 
which  procedures  will  consume  considerable  unnecessar.y  time.  The  most  con- 
venient way  to  get  the  water  into  the  vat  is  to  conduct  it  through  pipes,  either 
directly  from  a  pump  or  from  an  elevated  tank  used  for  storing  water  for  farm 
purposes.  Frequently,  however,  it  is  not  possible  to  bring  the  water  to  the  vat 
through  pipes,  and  it  becomes  necessary  to  resort  to  the  laborious  process  of 
hauling  it  in  barrels  on  wagons  or  sleds. 

"In  case  the  pine  tar  is  added  to  the  concentrated  solution  when  it  is  made, 
in  which  case,  as  already  stated,  it  is  necessary  to  dilute  the  solution  at  once, 
the  vat  should  be  partly  filled  with  water  and  then  the  arsenical  solution  added 
as  it  is  made.  For  example,  if  the  vat  holds  2000  gallons,  about  1500  gallons 
of  water  should  be  placed  in  the  vat,  then  four  times  the  amount  of  solution  for 
making  500  gallons  of  dip  should  be  prepared  and  mixed  with  the  water,  after 
which  the  vat  should  be  filled  to  the  2000-gallon  mark.  Within  certain  limits 
it  is  immaterial  just  how  much  water  is  added  at  first,  provided,  of  course,  ample 
allowance  is  made  for  the  volume  of  the  concentrated  dip  so  that  when  it  is 
added  the  dip  line  will  not  come  above  the  mark  to  which  the  vat  is  to  be  filled. 

"The  capacity  of  the  vat  at  a  depth  of  5  feet  3  inches  is  1470  gallons.  In 
order  to  fill  it  to  that  depth  with  dip  it  will  be  necessary  to  prepare  two 
batches  of  concentrated  dip,  each  containing  the  ingredients  necessary  for  mak- 
ing 500  gallons  of  diluted  dip,  and  a  third  batch  containing  7  pounds,  9  ounces 
of  arsenic  and  22  pounds,  3  ounces  of  sodium  carbonate  in  case  8  pounds  of 
arsenic  are  being  used  to  the  500  gallons,  or  9  pounds,  7  ounces  of  arsenic  and 
22  pounds,  S  ounces  of  sodium  carbonate  in  case  10  pounds  of  arsenic  are  being 
used  to  the  500  gallons. 

"The  arsenical  dip  may  be  left  in  the  vat  and  used  repeatedly,  replenishing 
it  with  the  proper  quantities  of  water  and  stock  solution  when  necessary.  When, 
however,  the  dip  becomes  filthy  through  the  addition  of  manure  and  dirt  carried 
in  by  the  cattle,  the  vat  should  be  emptied,  cleaned,  and  filled  with  fresh  fluid. 
The  frequency  with  which  this  should  be  done  must  be  left  to  the  owner,  as  the 
condition  of  the  dip  at  any  period  after  it  has  been  made  depends  on  a  variety 
of  conditions,  such  as  the  number  of  cattle  dipped,  and  the  frequency  of  the 
dippings,  etc.  Even  though  the  dip  may  not  become  very  filthy,  its  efficiency 
decreases  somewhat  on  standing,  owing  to  gradual  oxidation  of  the  arsenic.  It 
is  therefore  advisable  to  recharge  the  vat  at  intervals  irrespective  of  the  con- 
dition of  the  dip  to  cleanliness." 


THE  TICKS  311 

Precautions.  —  From  the  time  the  arsenic  is  purchased  to  the  final 
disposal  of  the  old  dip,  great  care  should  be  exercised  in  storing,  handling 
and  using  the  same  owing  to  the  very  poisonous  nature  of  the  chemical. 
"  Cattle  should  always  be  watered  a  short  time  before  they  are  dipped. 
After  they  emerge  from  the  vat  they  should  be  kept  on  a  draining  floor  un- 
til the  dip  ceases  to  run  from  their  bodies  ;  then  they  should  be  placed  in 
a  yard  free  of  ^■egetation  until  they  are  entirely  dry.  If  cattle  are  al- 
lowed to  drain  in  places  where  pools  of  dip  collect  from  which  they  may 
drink,  or  are  turned  at  once  on  the  pasture,  where  the  dip  will  run  from 
their  bodies  on  the  grass  and  other  vegetation,  serious  losses  are  liable  to 
result.  Crowding  the  animals  before  they  are  dry  should  also  be  avoided, 
and  they  should  not  be  driven  any  considerable  distance  within  a  week 
after  dipping,  especially  in  hot  weather.  If  many  repeated  treatments 
are  given,  the  cattle  should  not  be  treated  oftener  than  every  two  weeks. 

"  In  addition  to  properly  protecting  vats  containing  arsenical  dip 
when  not  in  use  another  precaution  must  be  observed  when  vats  are 
to  be  emptied  for  cleaning.  The  dip  should  not  be  poured  or  allowed  to 
flow  on  land  and  vegetation  to  which  cattle  or  other  animals  have  access. 
The  best  plan  is  to  run  the  dip  into  a  pit  properly  protected  by  fences. 
The  dip  should  also  not  be  deposited  where  it  may  be  carried  by  seepage 
into  wells  or  springs  which  supply  water  used  on  the  farm." 

Procedure.  —  After  having  exercised  the  precaution  of  watering 
them,  the  cattle  to  be  dipped  are  driven  from  a  pen  one  by  one  into 
the  chute  and  thence  into  the  dip  (Fig.  192).  The  plunge  is  likely  to 
wet  the  animal  all  over,  but  a  second  plunge  of  the  head  into  the  dip 
near  the  middle  of  the  vat  by  means  of  a  forked  stick  is  advised  so  that 
the  head  is  really  plunged  under  twice  in  passage  through  the  dip. 
After  drying,  the  cattle  should  be  driven  on  to  a  tick-free  pasture  and 
the  process  repeated  in  from  seven  to  ten  days  in  order  to  destroy  all 
ticks  which  may  have  escaped  the  action  of  the  first  dipping. 

Pasture  Rotation.  —  Exterminating  ticks  by  pasture  rotation  is 
based  on  the  time  required  to  kill  the  ticks  by  starvation.  Inasmuch 
as  the  longevity  of  ticks  depends  on  moisture  and  temperature  mainly, 
local  conditions  affecting  the  same  must  be  taken  into  consideration. 
Cold  and  moisture  prolong  life,  while  dryness  and  heat  shorten  the  same. 

In  pasture  rotation  the  cattle  are  kept  off  of  a  given  pasture  for  a 
given  length  of  time,  after  which  they  are  moved  to  a  third  area,  etc., 
until  all  ticks  have  matured  and  have  dropped  from  the  cattle  and 
have  died  from  starvation  on  the  earlier  plots.  Thus  a  field  should  be 
divided  into  three  or  more  plots  each  separated  by  means  of  two  fences 
about  fifteen  feet  apart  to  reduce  the  opportunity  of  ticks  to  crawl 
from  one  plot  to  the  other. 

Various  plans  requiring  from  four  and  a  half  to  eight  months  have 
been  devised  to  free  both  cattle  and  pasture  from  ticks.  Thus  a  plan 
requiring  four  and  one  half  months  is  described  by  Gray  bill  (1912,  he. 
cit.)  (Fig.  193).     He  advises  dividing  the  pasture  in  the  middle  by  two 


312        MEDICAL  AND   VETERINARY  ENTOMOLOGY 


THE  TICKS 


313 


Fino  ND.3. 
CORN. 
COWPEAS. 


NOVIUOyETHEHERD  JO 
FIELD  mi  A. 


FIELD  NOA. 
COTTON- 
RYE  m  CRIUSON 
GLOVER. 


lines  of  temporary  fence  fifteen  feet  apart.  This  to  be  done  some  time 
in  the  spring.  The  herd  is  first  kept  in  field  No.  lA,  and  is  then  re- 
moved, on  June  15,  to  field  No.  IB,  and  on  September  1  to  field  No. 
2A.  The  cattle  must  remain  twenty  days  on  fields  2A,  2B,  and  3. 
At  the  end  of  this  time,  which  would  be  November  1,  all  the  ticks  will 
have  dropped  and  the  herd  is  returned  to  field  No.  lA,  which  has  be- 
come free  from  ticks  in  the  meantime.  Field  No.  IB  becomes  free 
from  ticks  July  1  of 
the  following  year, 
when  the  double  fence 
between  lA  and  IB 
may  be  removed  and 
the  cattle  may  then 
(and  not  before)  graze 
over  both  fields.  By 
August  1  the  entire 
farm  will  be  free  from 
ticks. 

Graybill  advises 
as  above  that  double 
fences  be  built  be- 
tween all  the  fields, 
when  practicable,  in 
order  to  prevent  ticks 
from  getting  from 
one  field  to  another. 
In  place  of  the  extra 
line  of  fence  the  next 
best  thing  would  be 
to  "  throw  up  several 
furrows  with  a  plow 
on  each  side  of  the 
dividing  fences."  If 
streams  run  through 
the  farm  or  the 
slope  of  the  land  is 
considerable,  so  that  ticks  may  be  washed  from  field  to  field,  he  ad- 
vises arranging  the  fields  so  that  drainage  is  from  field  No.  lA  to  No. 
IB,  and  from  No.  3  toward  fields  Nos.  2A  and  2B. 

African  coast  fever,  also  known  as  Rhodesian  red  water,  occurs 
along  the  east  coast  of  Africa,  including  Rhodesia  and  the  Transvaal. 
The  mortality  is  said  to  range  close  to  90  per  cent.  The  causative 
organism  is  Theileria  parva  (Theiler).  The  symptoms  of  the  dis- 
ease, according  to  Robertson,^  are  described  as  follows :    "  These  are 


FiaO  NO.ZB. 
OCT.  IZ  MOVE  THE  HERD . 
TO  FIEID  m.S. 


OATlFgtMMt^  By__ 
cq^vpeasor  ithbr 

EDRAa,'. 


FiEinmzA. 

SEFTZZMDVETHE 
HERD  TO  FIELD 
NO.Z  B. 


mm 

HOJSl- 

'Ill/nil 


PASTURE :  BERMm    YEkfl^  AND  BURRCLDifER. 
I    I 

FIELD  m.lB. 

...  .^  riFU, 

LS    I 


SEPrZ.MOI/ETyEMERD  TO  FIELD 


WILL  BE  E'rEE  of  TICKS  AHD  7HE\ 
Wporkryooublf  rtmE*<AYB£\ 

REMOIfE'D.  I 


TE, 


FIRD  NOIA- 
yUAIEIS.Mon  THE  HERD  TO  F/ELD 
^MOIB.  KEEP  PUT  ALL    Afl/IMULS 
[EROM  THIS  DATE  UffTIL  NDU.UHCA/ 
\THIS FIELD  WILL  BE  ERes  OF  TICKS. 
I 
1 


Fig.  193.  —  Plan  for  freeing  cattle  and  pastures  from  ticks 
by  rotation,  requiring  four  and  one  half  months.  (Re- 
drawn after  Graybill.) 


1  Robertson,  W.,  1904. 
of  Agr.  Bull.  18. 


African  coast  fever.     Cape  of  Good  Hope,  Dept. 


314        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

neither  very  definite  nor  characteristic.  The  disease  runs  its  course  in 
from  twelve  to  fifteen  days,  dating  from  the  time  the  animal  is  first 
noticed  sick.  The  temperature  is  high,  106°  to  107°  F.  There  is  run- 
ning from  the  eyes  and  nose,  and  symptoms  of  pain  in  the  abdomen. 
Purging  and  diarrhea  are  frequently  seen.  In  the  later  stages  the  dung 
may  contain  blood  and  be  dark  in  color.  The  animal's  brain  usually 
becomes  affected  before  death,  which  is  preceded  by  stupor  and  coma. 
If  the  lungs  become  involved  there  is  great  distress  in  breathing,  ac- 
companied by  a  short  cough."  Lounsbury's  ^  experiments  demon- 
strate that  African  coast  fever  may  be  transmitted  to  susceptible 
cattle  from  actually  sick  ones  through  the  medium  of  five  species  of 
ticks  of  the  genus  Rhipicephalus,  namely  R.  appendiculatus,  R.  evertsi, 
R.  simus,  R.  capensis,  and  R.  nitens.  He  succeeded  in  transmitting  the 
disease  from  twelve  sick  animals  to  thirty-five  healthy  ones  by  means 
of  ticks.  The  infection  was  taken  by  ticks  in  one  stage  of  the  life  history 
and  transmitted  in  the  next  following  stage.  A  dozen  or  more  ticks 
were  usually  applied  in  each  case ;  however  he  succeeded  in  infecting 
an  animal  with  one  tick  alone  and  in  another  case  by  two  ticks.  The 
ticks  are  believed  to  be  in  constant  readiness  to  transmit  infection. 
The  incubation  period  was  found  to  average  thirteen  and  one-half 
days  and  ranged  from  nine  to  nineteen  days.  While  the  duration  of 
the  cases  averaged  twelve  days,  it  was  found  that  few  of  the  animals 
appeared  seriously  ill  until  a  few  days  before  death,  an  important  factor 
in  the  dissemination  of  the  disease  in  the  veldt  during  the  time  that  the 
infective  animal  is  active. 

Other  important  discoveries  were  that  the  disease  did  not  result 
from  ticks  fed  on  recovered  animals,  neither  from  the  progeny  of  ticks 
from  sick  animals,  nor  from  adults  which  as  nymphs  had  fed  on  im- 
mune animals,  but  as  larvse  had  fed  on  sick  animals. 

Spotted  Fever.  —  Spotted  fever  has  been  known  in  the  Bitter  Root 
Valley  of  Montana  (U.  S.  A.)  since  1872,^  also  known  as  "tick  fever," 
"black  fever,"  "blue  disease,"  "black  measles,"  and  " piroplasmosis 
hominis."  The  causative  organism  is  doubtfully  referred  to  as  Piro- 
plasma  hominis  (Wilson  and  Chowning).  The  most  characteristic  and 
constant  symptom  is  the  eruption  which  appears  about  the  second  to 
the  fifth  day  on  the  wrists,  ankles  and  back,  later  spreading  to  all  parts 
of  the  body  and  lasting  from  a  few  days  (8  to  21)  to  several  months : 
"  These  spots  are  petechial  and  not  raised  ;  at  first  they  are  rose-colored 
and  disappear  momentarily  upon  pressure ;  but  later  they  become  per- 
manent and  assume  a  dark  blue  or  purplish  color ;  they  may  coalesce 
and  give  a  mottled  or  marbled  appearance  to  the  skin ;    they  may  or 

1  Lounsbury,  Chas.  P.,  1906.  Ticks  and  African  coast  fever.  Agrie. 
Journ.  of  the  Cape  of  Good  Hope,  Vol.  XXVIII,  No.  5,  pp.  634-654. 

2  Stiles,  Ch.  Wardell,  1905.  A  zoological  investigation  into  the  cause, 
transmission  and  source  of  Rocky  Mountain  "spotted  fever."  Treasury 
Dept.  Public  Health  and  Marine  Hospital  Service  of  the  United  States.  Hygiene 
Lab.  Bull.  No.  20,  pp.  121. 


THE  TICKS  315 

may  not  be  tender  to  the  touch.  .  .  .  The  fever  develops  rapidly, 
and  may  register  102°  to  104°  or  105°  F.,  when  the  patient  takes  to 
bed.  It  gradually  reaches  its  maximum  in  two  to  seven  days,  when  it 
ordinarily  registers  103°  to  106°. 

"  Both  sexes  and  all  ages  are  subject  to  the  disease,  but  it  is  more 
common  in  males  from  21  to  40,  and  in  females  from  11  to  40  years  of 
age,  than  at  other  times  of  life.  ...  A  lethality  of  70.5  per  cent  was 
shown  for  139  collated  cases  .  .  .  100  per  cent  for  all  patients  over  60 
years  old.  So  far  as  one  could  judge  occupation  seems  to  play  a  role, 
for  a  very  large  percentage  of  the  patients  are  on  farrns  or  are  connected 
with  the  lumbering  industry  "  (Stiles,  1905,  loc.  cit.). 

In  Idaho  a  mild  type  of  the  disease  exists,  with  a  mortality  of  about 
1  to  3  per  cent  according  to  Stiles  and  from  5  to  7  per  cent  according 
to  Hunter  and  Bishopp. 

Tick  Transmission  of  Spotted  Fever.  —  After  a  preliminary  inves- 
tigation Wilson  and  Chowning  ^  in  1902  advanced  for  the  first  time  the 
theory  that  a  tick  ("wood  tick")  acts  as  the  natural  vector  of  the  dis- 
ease. According  to  Rickette  (in  48th  Biennial  Kept.  Montana  State 
Board  of  Health,  p.  106)  as  recorded  by  Hunter  and  Bishopp  ^  "  the 
first  experiments  which  resulted  in  the  proof  of  the  transmission  of 
spotted  fever  by  a  tick  were  conducted  by  Doctors  McCalla  and  Brere- 
ton  of  Boise,  Idaho,  in  1905.  In  these  experiments  a  tick  which  was 
found  attached  to  a  spotted  fever  patient  was  r^emoved  and  allowed  to 
bite  a  healthy  person.  In  eight  days  this  person  developed  a  typical 
case  of  spotted  fever.  The  experiment  was  continued  by  allowing  the 
same  tick  to  bite  a  second  person.  In  this  case  again  a  typical  case  of 
spotted  fever  resulted." 

The  famous  experiments  of  Doctor  H.  T.  Ricketts  began  in  April, 
1906.  The  more  important  published  work  of  this  lamented  investi- 
gator has  been  brought  together  in  a  memorial  volume  ^  from  which 
the  following  summary  is  made  of  his  reports  on  spotted  fever.  First 
of  all  it  was  shown  that  the  disease  could  be  transmitted  to  guinea  pigs 
by  direct  inoculation  and  that  the  duration  of  the  fever  and  cutaneous 
phenomena  resembled  very  closely  the  conditions  as  observed  in  humans. 
Hence,  knowing  the  susceptibility  of  this  species,  it  was  used  for  further 
experimentation. 

On  June  19,  1906,  a  small  female  tick  was  placed  at  the  base  of  the 
ear  of  a  guinea  pig  inoculated  intraperitoneally  June  11  with  3  cc.  of 
defibrinated  blood  of  a  spotted  fever  patient.     The  tick  fed  for  two 

1  Wilson,  Louis  B.,  and  Chowning,  William  M.,  1902.  The  so-called 
"spotted  fever"  of  the  Rocky  Mountains.  A  preliminary  report  to  the  Mon- 
tana State  Board  of  Health.  Journ.  Amer.  Med.  Assoc,  Vol.  39,  No.  3,  pp. 
131-136. 

2  Hunter,  W.  D.,  and  Bishopp,  F.  C,  1911.  The  Rocky  Mountain  spotted 
fever  tick.     U.  S.  Dept.  of  Agric,  Bur.  of  Ento.  BuU.  105,  pp.  47. 

3  Ricketts,  H.  T.,  1911.  Contributions  to  Medical  Science.  The  Univer- 
sity of  Chicago  Press.     497  pp.     (See  pp.  278-450.) 


316        MEDICAL  AND   VETERINARY  ENTOMOLOGY 


days  on  this  animal  and  was  then  removed  and  kept  for  two  days  in  a 
pill  box  and  on  June  23  placed  at  the  base  of  the  ear  of  a  healthy 
guinea  pig,  the  former  animal  dying  on  the  same  day  with  characteristic 
symptoms.  On  June  28  the  second  guinea  pig  showed  a  decided  rise 
in  temperature,  which  continued  high  until  July  5  and  became  normal 
on  July  7.  Proper  controls  were  conducted  and  two  guinea  pigs  which 
were  in  the  same  cage  with  the  tick-bitten  guinea  pig  for  two  weeks 
did  not  become  infected,  indicating  that  mere  association  did  not 
result  in  contracting  the  disease. 

In  addition  to  many  other  successful  experiments  during  the  follow- 
ing year  Ricketts  found  that  the  disease  can  be  transmitted  by  the 
male  as  well  as  by  the  female  tick  and  that  "  one  attack  of  the  disease 
establishes  a  rather  high  degree  of  immunity  to  subsequent  inocula- 
tion."    Furthermore  a  collection  of  ticks  taken  in  the  field  transmitted 

the  disease  to  a  guinea  pig 

in  the  laboratory,  indicat- 
ing the  fact  that  infective 
ticks  occur  in  nature  in 
probably  small  numbers. 

It  was  also  ascertained 
that  "  the  disease  may  be 
acquired  and  transmitted 
...  by  the  tick  during 
any  of  the  active  stages 
.  .  ,  and  that  the  larvae  of 
an  infected  female  are  in 
some  instances  infective. 
.  .  .  The  disease  proba- 
bly is  transferred  through 
the  salivary  secretion  of 
the  tick,  since  the  salivary 
glands  of  the  infected  adult  contain  the  virus."  The  transmission  is 
believed  to  be  "  biological  rather  than  purely  mechanical." 

Experiments  conducted  by  Moore  (Ricketts,  1911,  loc.  cit.,  pp.  428- 
436)  show  that  the  "  minimum  duration  of  feeding  necessary  for  a  tick 
to  infest  a  guinea  pig  was  one  hour  and  forty-five  minutes.  The  aver- 
age time  necessary  seems  to  be  about  ten  hours,  while  twenty  hours 
were  almost  constantly  infective."  Maver  (see  Ricketts,  1911,  loc.  cit., 
pp.  440^44)  in  a  series  with  other  species  of  ticks  found  that  spotted 
fever  can  be  transmitted  from  infected  to  normal  guinea  pigs  by  Der- 
macentor  variabilis,  Dermacentor  marginatus  and  Amblyomma  ameri- 
canum,  in  addition  to  Dermacentor  venustus. 

Ricketts'  careful  observations  with  regard  to  the  causative  organ- 
ism failed  to  substantiate  the  findings  of  Wilson  and  Chowning  that  the 
disease  is  of  piroplasmic  origin,  although  he  failed  to  secure  infective 
virus  by  passing  serum  diluted  tenfold   in   physiologic   salt   solution 


Fig.  194.  —  The  spotted  fever  tick,  Dermacentor 
venustus;  male  (left),  unengorged  female  (right). 
X  3.5. 


THE  TICKS  317 

through  a  Berkefeld  filter.  This  he  states  "  suggests  that  the  organism, 
though  undoubtedly  minute,  is  of  such  size  that  it  should  be  recognized 
by  the  use  of  high  magnifications,  or  that  it  is  of  peculiar  form  or  possesses 
such  adhesive  properties  that  it  is  not  readily  filterable." 

Rocky  Mountain  Spotted  Fever  Tick.  —  The  spotted  fever  tick, 
Dermacentor  venustus  Banks  (Fig.  194),  possesses  the  general  characters 
of  the  genus  Dermacentor,  viz.,  "  Usually  ornate,  with  eyes  and  festoons ; 
with  short,  broad  or  moderate  palps  and  basis  capituli  rectangular 
dorsally.  In  some  species  coxse  I  to  IV  of  the  male  increase  progres- 
sively in  size;  in  all  species  coxa  IV  is  much  the  largest;  the  male, 
moreover,  shows  no  ventral  plates  or  shields.  Coxa  I  bifid  in  both 
sexes.     Spiracles  sub-oval  or  comma-shaped  "  (Nuttall,  1911,  loc.  cit.). 

The  species  is  described  by  Banks,^  viz. : 

"Male  —  red  brown,  marked  with  white,  but  not  so  extensively  as  in  D.  oc- 
cidentalis,  usually  but  little  white  on  the  middle  posterior  region;  legs  paler 
red-brown,  tips  of  joints  whitish.  Capitulum  quite  broad,  its  posterior  angles 
only  slightly  produced;  palpi  very  short  and  broad,  not  as  long  as  width  of 
capitulum.  Dorsum  about  one  and  two-thirds  or  one  and  three-fourths  times 
as  long  as  broad,  with  many,  not  very  large,  punctures ;  lateral  furrows  distinct. 
Legs  of  moderate  size,  hind  pair  plainly  larger  and  heavier,  and  with  the  teeth 
below  distinct.  Coxae  armed  as  usual,  the  coxa  IV  nearly  twice  as  wide  at  base 
as  long.  Stigmal  plate  with  a  rather  narrow  dorsal  prolongation,  with  large 
granules  on  the  main  part  and  minute  ones  on  the  prolongation. 

"Length  of  male,  3.5  to  5  mm. 

"Female  —  Capitulum  and  legs  reddish  brown,  the  latter  with  tips  of  joints 
whitish;  shield  mostly  covered  with  white,  abdomen  red-brown.  Capitulum 
rather  broad,  posterior  angles  but  little  produced,  the  porose  areas  rather  large, 
egg-shaped,  and  quite  close  together;  palpi  shorter  than  width  of  capitulum. 
Shield  as  broad  as  long,  broadest  slightly  before  the  middle,  and  rather  pointed 
behind,  with  numerous,  not  very  large  punctures.  Legs  of  moderate  size,  the 
coxae  armed  as  usual.  The  stigmal  plate  has  a  rather  narrow  dorsal  prolonga- 
tion, with  large  granules  on  the  main  part,  and  small  ones  on  the  prolongation. 

"Length  of  female  shield,  2  mm." 

Life  History  and  Habits  of  Spotted  Fever  Tick.  —  The  most  com- 
plete and  satisfactory  study  of  the  habits  and  life  history  of  this  species 
has  been  made  by  Hunter  and  Bishopp  (loc.  cit.),  from  whose  work  the 
following  account  is  taken.  The  winter  is  passed  by  the  ticks  as  un- 
engorged  males,  females  and  nymphs.  They  begin  attacking  their 
warm-blooded  hosts,  including  man,  about  March  15  and  continue  so 
doing  to  about  July  15.  During  this  period  the  female  deposits  eggs. 
The  overwintering  nymphs  transform  to  adults  during  the  summer  and 
autumn  and  pass  the  winter  in  an  unengorged  condition,  thus  requiring 
about  two  years  for  their  development.  As  much  as  three  years  may 
be  required  for  complete  development  under  unfavorable  conditions. 

The  engorged  females  after  being  fertilized  drop  from  the  host 

1  Banks,  Nathan,  1908.  A  Revision  of  the  Ixodoidea,  or  Ticks,  of  the 
United  States.  U.  S.  Dept.  of  Agr.  Bur.  of  Ento.  Technical  Series,  No.  15, 
61  pp. 


318        MEDICAL  AND   VETERINARY   ENTOMOLOGY 

animal  and  deposit  about  4000  eggs  within  thirty  days,  beginning  to 
deposit  as  early  as  the  seventh  day  after  dropping.  The  eggs  are  ovoid, 
brownish  in  color  and  about  one  thirty-eighth  of  an  inch  long.  The  in- 
cubation period  ranges  from  thirty-four  to  fifty-one  days  in  the  Bitter 
Root  Valley  (15-41  days  at  Dallas,  Texas) .  The  newly  emerged  hexapod 
seed  ticks  shortly  after  hatching  crawl  up  blades  of  grass  or  other  objects 
and  await  the  coming  of  a  host,  usually  one  of  the  smaller  species  of 
rodents,  e.g.  ground  squirrels,  chipmunks,  woodchucks,  pine  squirrels 
and  wood  rats. 

After  attaching  to  the  host  the  larvfe  become  filled  with  blood  in 
from  three  to  eight  days,  after  which  they  drop  oft'  and  molt  in  from  six 
to  twenty-one  days,  emerging  from  this  stage  with  eight  legs,  —  a 
nymph.  Nymphs  emerging  from  the  larval  or  seed  tick  stage  late  in 
summer  or  autumn  pass  the  winter  as  nymphs,  others  find  a  second  host, 
either  a  small  mammal  or  less  commonly  a  larger  wild  or  domesticated 
animal.  The  feeding  period  requires  from  four  to  nine  days,  when  the 
engorged  nymphs  drop  to  the  ground  and  in  twelve  to  sixteen  days  and 
over,  molt  for  the  second  time,  emerging  as  adults. 

The  adults  now  by  preference  attach  themselves  to  larger  domesti- 
cated animals.  After  feeding  about  four  days  the  males  search  their 
mates,  mating  on  the  host  animal,  and  after  eight  to  fourteen  days  after 
attachment  the  engorged  females  drop  to  the  ground  and  deposit  their 
eggs  in  some  protected  place  near  by.  The  life  cycle  requires  two  years 
in  the  majority  of  cases;    however,  in  some  one  season  is  sufficient. 

The  fully  engorged  females  are  "  about  one  half  inch  long  by  one 
third  inch  wide  by  one  fourth  inch  thick.  On  account  of  the  enormous 
distention  of  the  back  part  of  the  body  of  the  female,  the  legs  and  head 
are  rendered  inconspicuous.  A  close  examination,  however,  will  show 
the  white  shield  on  the  back  just  behind  the  '  head.'  "  The  males  are 
about  the  same  size  as  the  females  before  engorgement,  and  have  the 
shield  (scutum)  covering  the  entire  back,  whereas  in  the  female  the 
shield  is  much  smaller  (Fig.  194). 

Longevity.  —  Hunter  and  Bishopp  (1911,  loc.  cit.)  have  "found 
that  all  unfed  seed  ticks  hatching  from  a  mass  of  eggs  usually  die  within 
one  month  after  the  first  eggs  hatch.  In  one  instance  a  period  of  117 
days  elapsed  between  the  beginning  of  hatching  of  the  eggs  and  the 
death  of  the  last  seed  tick,  (A  later  record  by  these  workers  exceeded 
317  days.)  Unfed  nymphs  have  been  found  to  survive  a  period  of  one 
year  and  eleven  days,  and  adults  collected  on  vegetation  during  the 
spring  months  may  survive  for  a  period  of  413  days  without  food." 

Distribution.  —  Bishopp  ^  states  that  the  northern  part  of  the 
Rocky  Mountain  region  of  the  United  States  is  the  territory  prin- 
cipally infested,  but  the  river  valleys  and  sagebrush  plains  in  the  west 
are  more  or  less  heavily  infested,  —  Idaho,  Wyoming,  Montana,  parts 

1  Bishopp,  F.  C,  1911.  The  Distribution  of  the  Rocky  Mountain  Spotted- 
fever  Tick.     U.  S.  Dept.  of  Agr.,  Bur.  of  Ento.  Circ.  No.  136. 


THE   TICKS  319 

of  Utah,  Colorado,  Nevada,  Oregon,  Washington,  California  and 
southern  British  Columbia  being  involved.  The  species  is  believed  to 
occur  in  greatest  numbers  between  3000  and  5000  feet. 

Control  of  Spotted  Fever  Tick.  —  Knowing  that  the  most  important 
agent,  if  not  the  sole  agent  under  natural  conditions,  in  the  dissemina- 
tion of  spotted  fever  is  Dermacentor  venustus,  it  becomes  evident  at 
once  that  the  control  of  this  tick  is  essential  to  the  control  of  the  disease. 

Since  the  principal  hosts  for  the  adult  stage  of  the  tick  are  the 
larger  domesticated  animals,  principally  horses  and  cows,  these  animals 
must  be  kept  free  from  ticks  by  the  application  of  ordinary  tick  control 
measures  (see  under  Texas  fever).  Because  the  tick  requires  at  least 
two  years  to  complete  its  life  history,  domesticated  animals  must  be 
kept  free  from  ticks  for  at  least  two  consecutive  years.  In  this  way 
maturity  is  prevented  and  no  eggs  will  be  deposited  to  furnish  a  new 
supply  of  seed  ticks  to  feed  on  smaller  rodents.  No  doubt  also  much 
exterminative  work  must  be  done  against  the  smaller  rodents,  as  well 
as  the  larger  wild  animals. 

The  most  significant  step  toward  the  control  of  spotted  fever  in 
Montana  was  taken  by  the  legislature  of  that  state  in  1913,  when  a 
bill  was  passed  creating  a  State  Board  of  Entomology,  with  authority 
to  act,  and  appropriating  $5000  per  annum  for  its  use  during  a  period  of 
two  years.     The  act  seems  so  significant  that  it  is  here  given  in  full : 

"An  Act  to  Create  the  State  Board  of  Entomology.  To  define  its  powers 
and  duties  and  appropriate  money  therefor. 

"Be  it  enacted  by  the  Legislative  Assembly  of  the  State  of  Montana. 

"Section  1.  There  is  hereby  created  the  Montana  State  Board  of  En- 
tomology, which  shall  be  composed  of  the  State  Entomologist,  the  Secretary 
of  the  State  Board  of  Health  and  the  State  Veterinarian. 

"Section  2.  The  Secretary  of  the  State  Board  of  Health  shall  be  Chairman 
of  said  Board  and  the  State  Entomologist  shall  be  Secretary. 

"Section  3.  None  of  the  members  of  said  Board  shall  receive  any  com- 
pensation other  than  that  already  allowed  by  law,  except  that  the  actual  expense 
of  members  while  engaged  in  the  duties  incident  to  the  work  of  said  board  shall 
be  paid  out  of  the  appropriation  made  to  carry  on  the  work  of  said  board. 

"Section  4.  It  shall  be  the  duty  of  said  board  to  investigate  and  study  the 
dissemination  by  insects  of  diseases  among  persons  and  animals,  said  investi- 
gation having  for  its  purpose  the  eradication  and  prevention  of  such  dis- 
eases. 

"Section  5.  Said  board  shall  take  steps  to  eradicate  and  prevent  the  spread 
of  Rocky  Mountain  tick  fever,  infantile  paralysis  and  all  other  infections  or 
communicable  diseases  that  may  be  transmitted  or  carried  by  insects. 

"Section  6.  Said  board  shall  have  authority  to  make  and  prescribe  rules  and 
regulations  including  the  right  of  quarantine  over  persons  and  animals  in  any 
district  of  infection  and  shall  have  the  right  to  designate  and  prescribe  the 
treatment  for  domestic  animals  to  prevent  the  spread  of  such  diseases ;  but  said 
board  shall  not  have  the  right  to  prescribe  or  regulate  the  treatment  given  to 
any  person  suffering  from  any  infectious  or  communicable  disease. 

"Section  7.  All  rules  and  regulations  of  the  State  Board  of  Entomology  shall 
be  subject  to  approval  by  tlie  State  Board  of  Health. 

"Section  8.  The  board  shall  publish  in  printed  form  all  rules  and  regulations 


320        MEDICAL  AND  VETERINARY  ENTOMOLOGY 

which  shall  be  adopted  by  said  board  for  the  eradication  and  control  of  diseases 
of  any  kind  and  such  rules  and  regulations  shall  be  circulated  among  the  resi- 
dents of  everj^  district  affected  thereby. 

"Section  9.  Any  person  who  shall  violate  any  of  the  rules  or  regulations  of 
the  State  Board  of  Entomology  shall  be  deemed  guilty  of  a  misdemeanor  and 
upon  conviction  thereof  shall  be  fined  in  any  sum  not  in  excess  of  one  himdred 
($100.00)  dollars,  or  by  imprisonment  in  the  County  Jail  for  any  period  not 
exceeding  thirty  (30)  days  or  by  both  such  fine  and  imprisonment. 

"Section  10.  There  is  hereby  appropriated  out  of  any  monej^s  in  the  State 
Treasury  not  otherwise  appropriated  the  sum  of  five  thousand  ($5000.00) 
dollars,  or  so  much  thereof  as  may  be  necessary  to  carry  on  the  work  of  the 
State  Board  of  Entomology  for  the  year  1913,  and  the  sum  of  five  thousand 
($5000.00)  dollars  or  so  much  thereof  as  may  be  necessary  to  carry  on  the  work 
of  said  board  for  Ihe  year  1914.  Said  money  to  be  expended  under  the  direc- 
tion and  approval  of  the  State  Board  of  Examiners. 

"Section  11.  All  Acts  or  parts  of  Acts  in  conflict  with  this  Act  are  hereby 
repealed. 

"Section  12.  This  Act  shall  take  effect  from  and  after  its  passage  and 
approval. 

"Approved  March  18,  1913." 

Other  Piroplasmoses.  —  At  least  two  types  of  piroplasmoses  are 
found  in  horses  and  mules,  namely  true  equine  piroplasmosis,  trace- 
able to  Babesia  cahalli  (Nuttall),  occurring  in  Russia,  Transcaucasia 
and  probably  Siberia,  and  secondly  a  similar  though  distinct  disease 
traceable  to  Nuttallia  equi  (Laveran)  occurring  in  Transcaucasia,  Italy, 
Africa,  India  and  South  America  (Brazil).  The  former  is  transmitted 
by  Dermacentor  reticulatus  while  the  latter  is  transmitted  by  Rhipiceph- 
alus  evertsi. 

Ovine  piroplasmosis  traceable  to  Babesia  ovis  (Babes)  occurs 
in  sheep  in  Transcaucasia,  Roumania,  Turkey  and  probably  also  in 
northern  Africa.  The  disease  is  carried  by  the  tick,  Rhipicephalus 
bursa. 

Canine  piroplasmosis,  also  known  as  "  malignant  jaundice  "  of  dogs, 
is  prevalent  in  Europe,  Asia  and  Africa.  The  causative  organism  is 
Babesia  canis  Plana  and  Galli-Valerio  and  the  carrier  is  Rhipicephalus 
sanguineus  in  India,  Europe  and  North  Africa ;  Hcemaphysalis  leachi 
is  the  carrier  in  other  parts  of  Africa. 

Tick  Paralysis.  — ■  A  very  striking  form  of  paralysis  induced  by  the 
bite  of  Dermacentor  venustus  has  been  reported  ^  as  occurring  in  both 
sheep  and  man  (children),  also  in  other  animals  (dog  and  rabbit),  in 
British  Columbia  and  Montana.  In  lambs  the  paralysis  develops 
gradually,  beginning  with  a  staggering  gait,  bumping  against  obstacles 
and  occasionally  falling,  finally  failing  to  rise.  The  attack  is  usually 
of  short  duration  but  may  persist  for  long  periods  and  may  terminate 
fatally.  The  symptoms  appear  in  from  six  to  seven  days  after  the  ticks 
have  become  attached.     It  is  believed  that  the  disease  is  "caused  by  the 

^  Hadwen,  Seymour,  1913.  On  "Tick  paralysis"  in  sheep  and  man  fol- 
lowing bites  of  Dermacentor  venustus.  Parasitology,  Vol.  VI,  No.  3,  pp.  293- 
297,  with  2  plates. 


THE   TICKS 


321 


inoculation  of  a  toxin  from  the  tick.  It  has  also  been  observed  that  the 
ticks  attach  themselves  by  preference  along  the  spinal  column  of  the 
host,  and  at  the  nape  of  the  neck  in  man. 

Other  Ixodine  Ticks.  —  Over  forty  species  of  ticks  (mostly  Ixo- 
dine)  are  known  to  occur  in  the  United  States  alone,  and  many 
other  species  occur  in  the  tropics. 
For  the  disease-bearing  and  ven- 
omous species  it  may  be  said 
that  a  single  individual  may  be  of 
great  importance,  while  the  eco- 
nomic importance  of  the  innocuous 
species  depends  on  relative  abun- 
dance. The  most  widely  distrib- 
uted and  abundant  genera  are 
Ixodes  and  Dermacentor.  Ixodes 
ricinus  Linn.,  commonly  called  the 
"  castor  bean  tick,"  is  found  in 
Europe,  America,  Asia  and  Africa, 
and  attacks  many  species  of  warm- 
blooded animals.  Ixodes  ricinus 
var.  californicus  Banks  (Fig.  195) 

is  commonly  found  in  California  on  the  black-tailed  deer,  the  bobcat 
and  other  species  of  wild  animals,  also  frequently  and  abundantly  on 
cattle.  The  common  "  dog  tick  "  or  "wood  tick"  also  attacks  many 
species  of  warm-blooded  animals,  among  them  horses,  cattle,  dogs  and 
man.  When  abundant  these  species  are  of  considerable  importance. 
In  the  eastern  part  of  the  United  States  Dermacentor  variabilis  Say 
is  the  most  common,  while  along  the  Pacific 
Coast  it  is  largely  replaced  by  Dermacentor  occi- 
^a^  dentalis  Neumann  (Fig.  196).     In  the  southern 

'^B^|-  part  of  the  United  States,  particularly  Texas  and 

y^^^m  \  Louisiana,    the    "lone    star  tick,"   Amhlyomma 

^^^^^H    '  americanuvi  Linn.   (Fig.   197)  is  very  common. 

^^B'  The    "  rabbit    tick,"     Hoemaphysalis    leporis  = 

^^^  palustris  Packard,  is  a  widely  distributed  and 

abundant  species  on  rabbits,  while  Rhipicephalus 


Fig.  195.  —  A  common  deer  and  cattle 
tick  of  California,  Ixodes  ricinus  var. 
californicus ;  female  (left),  male  (right). 
X3.5. 


Fig.  i96.-AVesterndog  Sanguineus  Latreille  is  known  as  the  "brown 
or  wood  tick,  Derwocen-  ^Qg  tick  "  and  is  almost  a  cosmopolitan  species. 
toroccideniaiis.     X  2.5.  N^^ttall  (1911,  loc.  cit.)  iucludcs  nine  genera 

in  the  family  Ixodidse,  namely  :  —  Ixodes,  Hsemaphysalis,  Dermacentor, 
Rhipicentor,  Rhipicephalus,  Margaropus,  Boophilus,  Hyalomma 
and  Amblyomma  (Aponomma).  "  Ixodes  is  clearly  marked  off  from 
the  other  genera  by  a  number  of  characteristics,  of  which  the  most 
striking  are  the  anal  groove  surrounding  the  anus  in  front  (Prostriata) 
and  the  absence  of  festoons.  The  remaining  genera  fall  naturally 
into   two  divisions :  the  one  characterized  by  a  comparatively  short. 


322        MEDICAL  AND   VETERINARY  ENTOMOLOGY 


and  the  other  by  a  comparatively  long,  capitulum."     Nuttall  further 
arranges  these  as  follows : 

Ixodidae 


Prostriata 


Metastriata 


Brevirostrata 


Longirostrata 


Group  1 

I 
1  Ixodes     2  Hsemaphysalis 


Group  1  Group  2 

I  I 

8  Hyalomma  9  Amblyomma 


Group  2 

3  Dennacentor 

4  Rhipicentor 

5  Rhipicephalus 
B  Margaropus 

7  Boophilus 

"  Ixodes :  inornate ;  without  eyes  and  without  festoons ;  spiracles 
round  or  oval ;  palpi  and  basis  capituli  of  variable  form ;  coxae  either 
unarmed,  trenchant,  spurred  or  bifid ;  tarsi  without  spurs.  Sexual 
dimorphism  pronounced,  especially  with  regard  to  the  capitulum;  in 
the  male  the  venter  is  covered  by  non-salient  plates  ;  one  pregenital,  one 
median,  one  anal,  two  adanal  and  two  epimeral  plates." 

"  Haemaphysalis :    inornate,  without  eyes  but  with  festoons ;    with 

usually  short  conical  palpi  whose 
second  articles  project  laterally 
beyond  the  basis  capituli,  which 
is  rectangular  dorsally.  With 
dorsal  process  on  first  trochanter. 
Usually  of  small  size  and  but 
slightly  chitinized.  Sexual  di- 
morphism slight.  The  male  shows 
no  ventral  plates  or  shields. 
Spiracles  in  male  usually  ovoid 
or  comma-shaped ;  in  female 
rounded  or  ovoid." 

"  Dermacentor :  usually 
ornate,  with  eyes  and  festoons ; 
with  short,  broad  or  moderate  palpi  and  basis  capituli  rectangular 
dorsally.  In  some  species  coxae  I  to  IV  of  the  male  increase  progres- 
sively in  size ;  in  all  species  coxa  IV  is  much  the  largest ;  the  male, 
moreover,  shows  no  ventral  plates  or  shields.  Coxa  I  bifid  in  both 
sexes.     Spiracles  suboval  or  comma  shaped." 

"  Rhipicentor :  inornate,  with  eyes  and  festoons ;  with  short 
palpi,  with  basis  capituli  hexagonal  dorsally  and  having  very  prominent 
lateral  angles.  Coxa  I  bifid  in  both  sexes.  The  male  resembles 
Rhipicephalus  dorsally,  Dermacentor  ventrally ;    coxa  IV  is  much  the 


Fig.    197.  —  The  lone   star  tick,    Amblyomma 
americanum.      X  3.5. 


THE  TICKS  323 

largest ;  no  ventral  plates  or  shields ;  spiracles  subtriangular  (female) 
or  comma-shaped  (male)." 

"  Rhipicephalus :  usually  inornate,  with  eyes  and  festoons; 
with  short  palpi  and  basis  capituli  usually  hexagonal  dorsally.  .  .  . 
Coxa  I  bifid.  The  male  possesses  a  pair  of  adanal  shields  and  usually 
a  pair  of  accessory  adanal;  some  males,  when  replete,  show  a  caudal 
protrusion.     Spiracles  bluntly  or  elongate  comma-shaped." 

"  Margaropus :  ^  inornate,  with  eyes,  but  without  festoons,  with 
short  palpi  and  capituhun  intermediate  between  that  of  Rhipicephalus 
and  BodphUus;  highly  chitinized,  the  unfed  adults  of  large  size.  The 
female  with  very  small  scutum.  Coxse  conical,  unarmed  but  for  a 
small  spine  posteriorly  on  coxa  I.  The  male  with  a  median  plate 
prolonged  in  two  long  spines  projecting  beyond  and  to  either  side  of 
the  anus ;  with  coxae  similar  to  those  of  the  female ;  legs  increasing 
progressively  in  size  from  pair  I  to  IV,  the  articles  especially  of  leg-pair 
IV  greatly  swollen.  When  replete,  the  male  shows  a  caudal  protrusion. 
Anal  groove  obsolete.     Spiracles  rounded  or  short-oval  in  both  sexes." 

"  Boophilus :  inornate,  wdth  eyes,  but  without  festoons;  with 
very  short  compressed  palpi  ridged  dorsally  and  laterally  ;  basis  capituli 
hexagonal  dorsally ;  slightly  chitinized ;  the  unfed  adults  of  small  size. 
Coxa  I  bifid.  Anal  groove  obsolete  in  female,  faintly  indicated  in  male. 
The  female  with  a  small  scutum ;  the  male  with  adanal  and  accessory 
adanal  shields.     Spiracles  rounded  or  oval  in  both  sexes." 

"  Hyalomma :  ornamentation  absent  or  present,  at  times  con- 
fined to  the  legs ;  with  eyes,  with  or  without  festoons,  with  long  palpi 
.  .  .  and  basis  capituli  subtriangular  dorsally.  The  female  approaching 
Amhlyomma.  The  male  with  a  pair  of  adanal  shields,  and  with  or  with- 
out accessory  adanal  shields  and  two  posterior  abdominal  protrusions 
capped  by  chitinized  points.     Coxa  I  bifid.     Spiracles  comma  shaped." 

"Amblyomma:  generally  ornate,  with  eyes  and  with  festoons. 
With  long  palpi,  of  which  article  2  is  specially  long ;  basis  capituli  of 
variable  form.  The  male  without  adanal  shields,  but  small  ventral 
plaques  are  occasionally  present  close  to  the  festoons.  Spiracles  sub- 
triangular or  comma-shaped"  (Nuttall). 

The  Argasine  Ticks 

Agas  persicus  Oken  =  A.  miniatus  Neumann  =  A.  americanus 
Packard,  a  cosmopolitan  fowl  tick,  is  one  of  the  most  important  poultry 
parasites  in  existence  (Fig.  198).  Other  than  "fowl  tick"  this  pest 
is  commonly  called  "  adobe  tick  "  or  "  tampan."  In  color  it  varies 
from  a  light  reddish  brown  to  a  dark  brown,  depending  on  the  stage 
of  engorgement.  In  size  the  obovate,  flattened  adults  average  about 
8.5  mm.  long  by  5.5  mm.  wide  in  the  female,  and  6.5  mm.  long   by 

1  Does  not  include  Margaropus  annulatus  =  BodphUus  annulatus. 

T 


324        MEDICAL  AND   VETERINARY  ENTOMOLOGY 


Fig.   198.  —  The  poultry  tick,  Aryas    (miniatus) 
persicus,  ventral  and  dorsal  views.       X  3.5. 


4.5  mm.  wide  in  the  male.  When  unengorged  their  thickness  is  about 
.75  mm.,  and  when  fully  engorged  may  be  nearly  3  mm.  at  the  thickest 
part.     The  edges  are  always  very  thin  even  when  engorged.     The  sexes 

are  not  easily  distinguish- 
able ;  the  males  are  smaller, 
but  may  be  as  large  as 
smaller  female  individuals, 
and  taper  slightly  more  an- 
teriorly, i.e.  are  more  obo- 
vate.  The  genital  orifice  of 
the  male  is  "  half-moon 
shaped,"  while  in  the  female 
it  is  "slit-like"  and  situated 
farther  forward,  i.e.  imme- 
diately behind  the  capitulum. 
The  capitulum  has  four  long 
hairs,  two  hypostomal,  and 
one  near  the  articulation  of 
each  palp,  all  directed  for- 
wards. The  palps  are  about  twice  as  long  as  the  hypostome,  second 
article  longest,  the  others  equal  in  length.  The  hypostome  has  6  or 
7  fine  denticles  on  each  half  distally,  followed  by  stout  teeth  |,  the 
numbers  increasing  to  |,  |,  f,  basally,  the  teeth  decreasing  in  size,  not 
attaining  the  external  border  nor  extending  beyond  half  the  length 
of  the  hypostome  (Xuttall). 

Life  history  and  habits.  —  The  nymphs  and  adults  of  Argas  persicus 
are  strikingly  active  at  night,  migrating  long  distances  to  find  their 
host,  and  hiding  in  an  inactive  condition  during  the  day.  The  writer 
has  observed  this  pest  in  vast 
numbers  hiding  beneath  the 
loose  bark  of  the  eucalyptus  tree 
in  California.  Occasionally  spe- 
cimens are  sent  in  with  the  in- 
quiry, "  are  they  parasites  of 
the  tree  or  do  they  attack 
roosting  chickens,  the  chickens 
seem  to  do  very  poorly,  yet  we 
find  nothing  on  them?"  At 
night  if  one  observes  some- 
what closely,  one  may  see  hordes 
of  these  ticks  climbing  up  the 
sides  of  the  chicken  coop  to  the  roosts  and  upon  the  fowls,  filling  up 
leisurely  with  blood  and  before  daybreak  departing  for  their  hiding 
places.  The  females  deposit  their  large  reddish  brown  eggs  in  the 
crevices  occupied  during  the  day.  The  eggs  are  laid  in  masses  of 
from  25  to  100,  more  or  less,  and  there  are  usually  several  layings. 


Fig. 


199.  —  Larva  of  the  poultry  tick,  Argas 
{miniatus)  persicus.       X  30. 


THE  TICKS  325 

once  after  each  meal.  Egg  deposition  occurs  very  readily  in  al- 
most any  sort  of  receptacle  in  which  the  ticks  may  be  kept  for 
observation.  Hatching  takes  place  in  from  three  to  four  weeks.  The 
larvfe  (Fig.  199)  are  six-legged  and  very  active,  attacking  a  host 
apparently  as  readily  by  day  as  by  night.  Once  attached  the  larvae 
feed  for  about  five  days,  occasionally  longer,  remaining  firmly  attached 
during  this  time.  When  fully  engorged  they  appear  like  little  reddish 
globules,  causing  severe  irritation.  At  the  end  of  this  feeding  period 
the  larvse  detach  themselves,  having  become  rather  flattened  in  the 
meantime  and  then  crawl  away  from  the  host,  hiding  in  some  convenient 
crevice  near  by.  The  larvae  molt  in  about  a  week,  when  the  fourth 
pair  of  legs  appears  and  they  are  now  in  the  first  nymphal  stage,  appear- 
ing like  miniature  adults.  Nocturnal  feeding  now  takes  place  and  in 
ten  or  twelve  days  another  molt  occurs  and  the  second  nymphal  stage 
is  reached.  Again  the  tick  attaches  itself,  being  now  able  to  engorge 
itself  in  about  an  hour ;  again  after  the  expiration  of  something  over  a 
week  a  third  molt  takes  place  and  the  adult  stage  is  reached.  The 
adults  are  able  to  engorge  themselves  in  from  20  to  45  minutes. 

•  Since  eggs  are  deposited  mainly  during  July  in  California,  the  adult 
stage  may  or  may  not  be  reached  before  the  rainy  season  begins,  and  the 
overwintering  stage  may  be  in  the  second  nymphal  condition  or  as 
adults,  appearing  in  pestiferous  numbers  early  during  the  following 
summer.  Hence  there  is  ordinarily  one  generation  of  ticks  per  year 
under  normal  conditions.  In  the  absence  of  a  host  this  species  mani- 
fests a  striking  longevity  of  a  year  and  over  (a  little  over  two  years 
according  to  Lounsbury). 

Damage  Done.  —  Each  tick  when  engorging  requires  considerable 
blood  to  become  replete,  hence,  when  myriads  of  these  parasites  attack 
fowls  great  quantities  of  blood  must  be  extracted.  The  writer  has 
known  of  chickens  being  picked  up  under  the  roost  in  the  morning  with 
no  apparent  cause  for  death,  and  believes  this  to  have  been  due  directly 
to  the  work  of  ticks.  Weakened  and  unthrifty  condition  of  a  flock  may 
be  traceable  solely  to  ticks.  Poultry  suffering  from  ticks  have  dull, 
ragged  plumage,  suffer  from  diarrhea,  are  weak  and  lay  poorly. 

Fowl  Spirochaetosis.  —  A  very  fatal  disease,  known  as  "  fowl  spiro- 
chaetosis,"  is  traceable  to  Spirochosta  marchouxi  Nuttall  =  Spirochceta 
gallinarum  Blanchard,  occurring  in  India,  Australia,  Brazil,  Egypt  and 
Persia,  and  is  no  doubt  very  widely  distributed.  The  disease  attacks 
chickens,  geese,  turkeys,  guinea  fowls  and  other  birds.  The  symptoms 
are  described  as  follows  : 

"  The  disease  begins  with  diarrhea,  followed  by  loss  of  appetite, 
the  birds  appearing  somnolent ;  the  feathers  being  ruffled  and  the  comb 
pale.  The  birds  cease  to  perch,  lie  down  with  the  head  resting  upon 
the  ground  and  death  takes  place  during  a  convulsive  attack.  At 
times  the  disease  runs  a  slower  course,  the  legs  become  paralyzed,  then 
the  wings,  and  the  bird  grows  thin  and  dies  in  eight  to  fifteen  days. 


326        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

Recovery  may  take  place,  but  it  is  rare  after  paralytic  symptoms  have 
appeared.  At  autopsy,  during  the  acute  period  of  the  disease,  the 
spleen  appears  much  enlarged  and  the  liver  swollen  with  more  or  less 
fatty  degeneration,  at  times  the  liver  is  dotted  with  focal  necroses.  In 
chronic  cases  both  these  organs  may  appear  atrophied.  The  blood  is 
fluid  and  dark.  Spirochsetes  are  plentiful  in  the  blood  until  shortly 
before  death,  and  they  disappear  as  recovery  sets  in  "  (Xuttall). 

Argas  persicus  has  been  proved  to  be  the  carrier  by  ]\Iarchoux  and 
Salimbeni,  Balfour,  Nuttall  and  others.  These  investigators  have 
found  that  when  this  tick  sucks  blood  from  an  infected  fowl 
the  spirochcBtes  multiply  within  the  body  of  the  same  when  kept  at 
from  30°  to  35°  C.  and  are  capable  of  transmitting  the  disease;  but 
when  they  are  kept  at  from  15°  to  20°  C.  they  fail  to  transmit  it.  How- 
ever, if  the  ticks  are  later  kept  in  the  higher  temperature  they  become 
infective.  The  spirochoBtes  are  transmitted  by  the  bite  and  the  ticks 
are  said  to  be  infective  for  six  months  or  more.  The  incubation  period 
in  the  fowl  is  from  four  to  nine  days. 

Combating  the  Fowl  Tick,  —  Henhouse  roosts  should  be  painted 
thoroughly  with  kerosene  or  gasoline  and  put  in  position  with  the  ends 
in  cups  of  crude  oil  or  tar  or  embedded  in  oil-soaked  waste,  or  suspended 
by  wires  from  the  ceiling.  Roost  poles  must  be  free  from  bark.  All 
old  nests  and  rubbish  should  be  burned,  and  the  interior,  especially 
crevices,  sprayed  liberally  with  kerosene.  Boiling  water  or  steam  may 
be  used  instead  of  kerosene.  A  repetition  of  the  procedure  once  every 
five  or  six  weeks  during  the  tick  season  is  recommended.  The  use  of 
considerable  crude  oil  in  and  about  the  houses  is  very  desirable.  Fowls 
should  not  be  permitted  to  roost  in  trees,  because  of  the  hiding  places 
afforded  the  ticks  beneath  the  bark,  particularly  when  loose. 

If- the  henhouses  can  be  ma'de  tight,  fumigation  with  sulphur  is 
useful,  using  about  five  pounds  per  1000  cu.  ft.  of  space. 

For  the  treatment  of  fowls  infested  with  larval  ticks,  an  ointment 
of  kerosene,  lard  and  sulphur  is  advised. 

Argas  reflexus  Fabr.,  commonly  known  as  the  "  pigeon  tick,"  dift'ers 
from  A.  persicus  in  that  the  body  narrows  rather  suddenly  toward  the 
anterior  end  and  that  the  thin  margin  is  flexed  upward.  The  capitu- 
lum  has  "  two  long  post-hypostomal  hairs  ventrally,  directed  forwards. 
Palps  with  articles  sub-equal,  the  third  the  shortest,  denticulated  hairs 
dorsally.  .  .  .  Hypostome  rounded  terminally,  some  small  denticles 
at  the  tip,  followed  by  f  stout  teeth  merging  into  f  to  f  progressively 
smaller  teeth  "  (Nuttall)". 

Other  species  of  Argas  are  A.  brumpti  Neumann,  A.  vespertilionis 
Latreille  and  A.  cucumerinus  Neumann. 

Ornithodorus  moubata  Murray  is  the  African  relapsing  fever  tick 
(Fig.  200),  sharing  in  part  the  characters  of  the  genus  Ornithodorus, 
viz. :  "  Body  flat  when  unfed,  but  usually  becoming  very  convex  on 
distention.     Anterior  end  more  or  less  pointed  and  hood-like.     Margin 


THE   TICKS  3'27 

thick  and  not  clearly  defined,  similar  in  structure  to  the  rest  of  the  in- 
tegument, and  generally  disappearing  on  distention.  Capitulum  sub- 
terminal,  its  anterior  portions  often  visible  dorsally  in  the  adult.  Disks 
present  or  absent;  but  when  present  not  arranged  radially  (see  Argas). 
Certain  fairly  constant  grooves  and  folds  on  the  venter,  namely,  a 
coxal  fold  internal  to  the  coxse,  a  supracoxal  fold  external  to  the  coxa?, 
a  transverse  pre-anal  and  a  transverse  post-anal  groove  or  furrow,  and 
a  post-anal  median  groove.     Eyes  present  or  absent." 

0.  moubata  occurs  only  in  Africa,  is  an  eyeless  species  with  a  specific 
arrangement  of  the  "  humps  "  on  the  protarsus  of  the  first  pair  of  legs, 
being  "  subequal  and  tooth-like."  The  adults  measure  from  8  to  11  mm. 
in  length  and  about  7  mm.  in  breadth.  ''  The  color  varies  from  dusty 
brown  to  greenish  brown  in  living  specimens  and  turns  reddish  or 
blackish  brown  in  alcohol."  Eggs  are  deposited  in  small  batches  of 
from  10  to  80  at  intervals  of  from  three  to 
fifteen  days  during  a  period  of  several  months. 
The  eggs  are  apparently  readily  deposited  in 
captivity  upon  sand,  as  the  writer  has  observed 
in  other  species  of  Ornithodorus.  Hatching 
takes  place  in  from  ten  to  fifteen  days  and  over, 
depending  on  temperature.  Experimentally 
at  least,  the  active  larvse  attach  themselves  to 
a  warm-blooded  host,  remaining  attached  for 
nearly  a  week,  when  they  become  disengaged 
and  molt,  the  nymph  now  appearing.  The 
nvmphs   feed  at   intervals,    molting    once  or     Fig.  200.  —  African  reiaps- 

•^  .    ^  ,  1  1       xi  \^^   a    a  ingiever  tick,  Ornithodorus 

twice  between  each  meal ;    there  ma\  be  O-y        mouhata.     x  3. 
molts    and    apparently    young    females    molt 

even  after  sexual  maturity  has  been  reached,  according  to  various 
observers,  and  individuals  may  remain  infective  for  over  a  year.  Well- 
man  has  observed  that  this  species  attacks  a  wide  range  of  animals 
besides  man,  notably  pigs,  dogs,  goats  and  sheep;  Nuttall  found  them 
to  feed  in  his  laboratory  on  rabbits,  mice,  rats,  monkeys  and  fowls. 

African  Relapsing  Fever  is  a  disease  of  man  occurring  in  Africa 
(Congo  Free  State,  Angola  and  elsewhere),  is  caused  by  SpirochcBta 
duttoni  Novy  and  Kiiapp  and  is  therefore  a  Sinrochcptosis .  The 
symptoms  are  described  by  Nuttall  (1908,  he.  cit)  viz. :  "  headache, 
(especially  at  the  back  of  the  head),  vomiting,  abdominal  pam  and 
purging,  with  severe  fever,  a  pulse  of  90-120,  dry  hot  skin,  congested 
eyes  and  shortness  of  breath.  After  a  period  of  fever  lasting  about  two 
days,  there  is  a  fall  of  temperature,  but  a  fresh  attack  soon  follows. 
These  relapses  occur  more  frequently  than  in  European  relapsing  fever, 
being  usually  5  to  G  in  number,  but  there  may  be  more.  The  attacks 
leave  the  patient  in  a  weak  condition  for  a  long  time  after  recovery, 
which  usuallv  follows,  but  death  occurs  in  about  6  per  cent  of  the  cases." 

Button  and  Todd  in  1905  and  R.  Koch  in  the  same  year  showed 


328        MEDICAL  AND   VETERINARY  ENTOMOLOGY 


that  Ornithodorus  moubata  is  a  common  and  probably  the  usual  carrier 
of  this  spirochete  disease.  Leishman  as  well  as  Nuttall  has  shown  that 
the  tick  is  infective  only  through  its  excreta  and  not  by  its  bite,  that  the 
clear  coxal  secretion  is  an  anticoagulant  and  non-infective.  The 
infection  is  hereditary  in  the  tick  as  in  Texas  cattle  fever,  and  what  is 
more  the  spirochsete  is  transmitted  to  at  least  the  third  generation  of 
ticks.  The  attack  of  fever  takes  place  in  the  human  in  from  5  to  10 
days  after  the  tick  has  bitten. 

Control.  —  Wellman's  ^  recommendations,   in   part,  to  the  govern- 
ment of  xVngola  for  the  control  of  African  relapsing  fever  are  as  follows  : 
"  (1)    The  tick  in  question  should  be  regularly  destroyed  in  crowded 
centers  by  disinfecting  native  houses,  barracks  and  other  permanent 
quarters,  and  by  burning  old  camps,  huts,  etc. 

"  (2)    Soldiers,  laborers  on  plantations,  etc.,  should  be  made  to  keep 

their  houses  clean  and  to 
sleep  in  hammocks,  or  on 
beds  well  raised  from  the 
floor  and  away  from  the 
wall.  Natives  should 
never  be  allowed  to  sleep 
in  or  near  the  quarters  of 
Europeans. 

"  (3)  Soldiers,  porters, 
servants,  plantation  la- 
borers and  other  control- 
lable bodies  of  natives 
should  be  compelled  to 
observe  regulations  re- 
garding regular  bathing 
and  washing  of  clothes." 
The  Spinose  Ear  Tick, 
Ornithodorus  megnini  Duges  (Fig.  201),  occurs  commonly  in  California 
and  other  subtropical  parts  of  the  United  States  and  Mexico.  It  re- 
ceives its  name  from  the  fact  that  the  nymph  is  covered  with  numer- 
ous spines  and  in  all  stages  the  tick  attacks  the  ears  of  cattle,  horses, 
mules  and  occasionally  other  domesticated  animals  and  man.  Rather 
large  dark  eggs  are  deposited  by  this  species  on  the  ground,  where 
the  seed  ticks  hatch  in  two  or  three  weeks  (as  short  as  eleven 
days  according  to  Hooker).^  Hooker  furthermore  states  that  the 
replete  females  creep  upwards  several  feet  before  ovulation  so  that 
the  larvae  upon  emerging  find  themselves  in  an  advantageous  position 


Fig.  201.  —  Spinose  ear  tick,  Ornithodorus  w.egnini. 
X  3.5. 


'    'l^Wellman,  F.  C,   1906.      Human    Trypanosomiasis   and  Spirochaetosis  in 
Portuguese  South-west  Africa  with  suggestions  for  preventing  their  spread  in 
the  colony.     Journ.  of  Hygiene  (Cambridge),  Vol.  VI,  No.  3,  pp.  237-245. 
►    ■    2  Hooker,  W.  A.,  1908.      Life  history,   habits  and  methods  of  study  of  the 
Ixodoidea.     Journ.  of  Econ.  Ento.,  Vol.  1,  No.  1,  pp.  34-51. 


THE  TICKS  329 

to  reach  the  head  and  enter  the  ears  of  the  host.  The  writer's  observa- 
tions, however,  indicate  that  the  eggs  are  at  least  commonly  deposited 
on  the  ground  and  that  the  larvae  crawl  up  weeds  and  other  vegetation 
as  do  other  seed  ticks  and  reach  the  host's  head  while  grazing.  The 
larvae  feed  in  the  deeper  folds  of  the  host's  ears  for  from  five  to  seven 
days,  molting  in  situ,  begin  feeding  again  as  nymphs,  continuing  their 
infestation  for  several  weeks  before  leaving  the  ears.  After  the  last 
molt,  which  occurs  about  seven  days  after  leaving  the  host  in  mid- 
summer or  early  autumn,  they  begin  depositing  eggs. 

Damage  Done.  —  The  writer  has  received  many  complaints  from 
various  cattle  grazing  districts  in  California  relative  to  the  "  ear  tick." 
Ears  are  occasionally  sent  in  thoroughly  infested  with  these  pests  in 
all  stages.  It  is  commonly  asserted  that  this  tick  is  responsible  for 
much  deafness  in  domesticated  animals,  and  it  is  also  believed  to  be 
responsible  for  illness  and  even  death,  particularly  in  calves. 

Treatment.  ■ —  Owing  to  the  position  occupied  by  the  ticks  on  the 
host  only  local  treatment  is  of  any  avail.  Good  results  are  ordinarily 
secured  by  flooding  the  ear  with  carbolated  olive  oil  or  linseed  oil,  which 
causes  the  parasites  to  vacate,  whereupon  they  may  be  easily  removed 
and  destroyed  by  crushing  or  placing  in  kerosene. 

Other  species  of  Ornithodorus.  —  Ornithodorus  savignyi  Audouin, 
occurs  in  Africa,  is  known  as  a  venomous  species  and  is  believed  to 
be  a  carrier  of  relapsing  fever;  Ornithodorus  coriaceus  C.  L.  Koch, 
known  as  the  "  Pajaroello,"  occurs  in  California  and  Mexico  and  is 
undoubtedly  one  of  the  most  venomous  species  of  ticks.  (See  Chapter 
XX.) 


CHAPTER  XIX 
MITES 

Class  Arachnida,  Order  Acarina 

Characteristics.  —  In  the  mites,  as  in  the  ticks,  the  abdomen  is 
broadly  joined  to  the  cephalothorax  with  httle  or  no  evidence  of  separa- 
tion. All  species  are  very  minute,  most  of  them  just  about  visible  to 
the  naked  eye.  The  mites  have  four  pairs  of  legs  as  have  other  Arach- 
nids, but  possess  only  three  pairs  (exceptionally  less)  as  larvae.  The 
mouth  parts  are  more  or  less  tick-like  and  are  fitted  for  piercing.  One 
or  more  pairs  of  simple  eyes  are  usually  present.  The  respiratory  system 
is  in  most  species  similar  to  that  of  the  ticks,  i.e.  tracheal.  Nearly  all 
species  deposit  eggs ;  however,  there  are  a  few  which  are  viviparous, 
among  them  Pediculoides.  From  the  egg  there  emerges  the  hexapod 
larva,  which  molts  shortly  and  then  presents  its  fourth  pair  of  legs. 
The  life  history  of  many  species  is  passed  in  less  than  six  weeks,  in  some 
as  short  as  two  weeks. 

An  infestation  of  mites  is  termed  acariasis.  Those  species  which 
burrow  into  the  skin,  producing  channels  and  depositing  therein  their 
eggs,  are  said  to  produce  sarcoj)tic  acariasis,  e.g.  Sarcoptes  scabiei  var. 
suis  of  swine  mange ;  while  those  species  which  deposit  their  eggs  at 
the  base  of  the  hairs  of  the  host  or  on  the  skin  and  pile  up  scabs,  are 
said  to  produce  psoroptic  acariasis,  e.g.  Psoroptes  communis  var.  ovis  of 
sheep  scab. 

A.  Mange,    or  Itch  Mites  —  Sarcoptic  Acariasis 
Family  Sarcoptidce 

Characters  of  Sarcoptidae.  —  All  members  of  the  family  Sarcoptidse, 
commonly  known  as  the  itch  mites,  mange  mites  or  scab  mites,  are  very 
small  (just  about  visible  to  the  naked  eye),  whitish  and  somewhat 
hemispherical  in  form.  Banks  ^  characterizes  this  family,  viz. :  "  The 
body  is  entire,  and  the  surface  transversely  striated  and  provided  with  a 
few  bristles,  often  short,  stout  and  sharp-pointed.  The  legs  are  short 
and  stout,  arranged  in  two  groups.  The  anterior  legs  are  usually  larger 
than  the  others.     The  tarsi  commonly  terminate  in  a  stout  claw.     There 

*  Banks,  Nathan,  1905.  A  treatise  on  the  Acarina,  or  mites.  Proc.  U.  S. 
National  Museum,  Smithsonian  Institution,  Washington,  D.C.,  Vol.  XXVIII, 
pp.  1-114. 

330 


MITES 


331 


is  generally  a  long  pedicellate  sucker,  sometimes  with  a  jointed  pedicel. 
The  claw  or  sucker  may  be  absent  and  in  its  place  a  long  bristle.  The 
legs  often  show  a  chitinous  framework  of  rings,  both  transverse  and 
oblique.  On  the  front  of  the  body  is  a  prominent  beak.  The  palpse 
are  small,  three-jointed  and  appressed  to  the  sides  of  the  beak  beneath. 
.  .  .  There  are  frequently  sexual  differences ;  some  males  have  the 
third  pair  of  legs  very  large  and  long,  while  the  fourth  pair  is  very  small. 
Sometimes  there  are  plate-like  lobes  at  the  tip  of  the  male  abdomen, 
and  the  tarsi  may  terminate  differently  in  the  two  sexes." 

The  family  Sarcoptidse  includes  a  number  of  important  genera, 
among  them  Sarcoptes,  Psoroptes,  Chorioptes,  Otodectes  and  Cnemi- 
docoptes. 

Mange  or  Itch  Mites.  —  The  mange  or  itch  mites  belong  to  the 
genus  Sarcoptes,  have  very  short  legs,  the  posterior  pair  not  extending 
beyond  the  margin  of  the  nearly  circular 
body  (Fig.  202) ;  suckers  are  present  on 
the  first  and  second  pair  of  legs.  The 
sarcoptic  mites  burrow  in  the  skin,  where 
they  produce  definite  burrows  in  which 
the  females  deposit  their  eggs. 

The  species  of  Sarcoptes  inhabiting 
the  skin  of  mammals  are  ordinarily  termed 
varieties  of  Sarcoptes  scahiei  L.,  the  dif- 
ferences being  very  slight  and  many  of 
them  may  interchange  hosts,  e.g.  Sarcoptes 
scahiei  var.  sids,  parasitic  on  swine  and 
on  man,  and  when  on  the  latter  is  known 
as  S.  scahiei  var.  hominis;  Sarcoptes  scahiei 
var.  equi  of  the  horse  is  also  parasitic 
on  man.  Given  parasites,  however,  ordi- 
narily exist  only  for  a  limited  time  on  an- 
other host. 

Human  Itch.  —  The  itch  mite  attack- 
ing humans  is  known  as  Sarcoptes  scahiei  var.  hominis.  It  attacks  by 
preference  the  thin  skin  between  the  fingers,  the  bend  of  the  knee  and 
elbow,  the  penis  and  other  parts  of  the  body,  producing  an  almost  in- 
tolerable itching.  Infestation  is  ordinarily  secured  by  direct  contact, 
hand  shaking,  etc. 

Life  History  of  Itch  Mite.  —  The  female  mites  deposit  their  rather 
large  oval  eggs  in  the  tortuous  tunnels  which  they  have  made  in  the 
epidermis.  From  10  to  25  eggs  are  deposited  by  each  individual. 
"  The  female,  having  deposited  her  complement  of  eggs,  dies  at  the  end 
of  her  burrow.  As  the  skin  of  the  host  is  always  wearing  off,  and 
constantly  being  renewed  from  below,  the  eggs,  when  ready  to  hatch, 
will  be  close  to  the  surface,  so  that  the  mites  may  readily  escape.  Above 
each  burrow  there  is  often  a  little  pimple,  containing  a  watery  fluid  " 


Fig.  202.  —  Showing  life  history 
and  general  characteristics  of  a 
typical  sarcoptic  (mange  or  itch) 
mite ;  egg  (lower  right)  ;  larva 
(lower  left)  ;  male  (upper  left)  ; 
female  (upper  right).  Sarcoptes 
scabiei  var.  suis.  the  itch  or  mange 
mite  of  swine.       X  57. 


332       MEDICAL  AND    VETERINARY  ENTOMOLOGY 

(Banks).  The  hexapod  larvae  hatch  in  three  or  four  days.  In  this 
stage  the  area  of  infection  is  most  rapidly  increased.  Maturity  is 
reached  in  ten  to  twelve  days,  during  which  time  there  are  said  to  be 
three  molts.  Gerlach,  according  to  Braun/  has  found  that  the  progeny 
reproduce  again  in  fifteen  days,  and  that  each  female  produces  about 
fifteen  individuals,  after  which  she  dies.  Hence  the  descendants  of 
one  pair  of  mites  in  three  months  would  number  1,500,000,  which  ac- 
counts for  the  rapid  spread  of  itch  on  the  individual  host. 

Treatment  of  Human  Itch.  —  Inasmuch  as  the  mites  are  protected 
in  their  tunnels  in  the  epidermis,  the  skin  must  be  thoroughly  softened 
with  soap  and  hot  water  before  a  remedy  is  applied.  Sulphur  ointments 
give  very  good  results  if  applied  repeatedly  at  intervals  of  three  or  four 
days.  Tar,  creolin,  balsam  of  Peru,  tincture  of  iodine,  etc.,  are  also 
used.  LInderclothing  coming  in  contact  with  the  parts  affected  should 
be  boiled.     Cleanliness  is  essential  to  prevent  infection. 

Swine  Mange.  —  Mange  of  swine  is  caused  by  Sarcoptes  scabiei  var. 
suis  (F'ig.  202),  which  resembles  Sarcoptes  scabiei  var.  hominis  very 
closely,  if  it  is  not  identical.  Mange  attacks  the  swine  commonly  about 
the  top  of  the  neck,  shoulders,  ears,  withers  and  along  the  back  to  the 
root  of  the  tail.  A  microscopical  examination  of  deeper  tissue  from 
beneath  scabs  will  usually  reveal  the  mites.  Comparatively  few  cases 
of  swine  mange  have  come  to  the  writer's  attention,  even  in  localities 
where  swine  raising  is  carried  on  extensively,  hence  it  seems  that  the 
disease  is  not  as  widespread  as  might  be  expected. 

Suckling  pigs  and  young  shoats  ordinarily  suffer  most.  The  affected 
animals  scratch  and  rub  vigorously,  which  may,  however,  be  due  to 
lice,  but  if  the  skin  is  cracked  and  thickly  encrusted  with  heavy  scabs, 
and  the  hair  stands  erect,  an  examination  for  scab  mites  should  be  made. 

Infected  animals  should  be  isolated  and  immediately  treated,  the 
quarters  should  be  disinfected  with  a  10  per  cent  creolin  solution,  1  to 
10  kerosene  emulsion,  1  to  15  lime  sulphur  solution  or  the  like. 

The  life  history  and  habits  of  the  swine  mange  mite  correspond  in 
every  respect  with  the  itch  mite  of  humans. 

Treatment  for  Swine  Mange.  —  In  the  treatment  of  swine  mange, 
it  is  necessary  to  apply  external  remedies,  in  addition  to  sanitary  pre- 
cautions to  prevent  spread  and  reinfection  of  treated  animals. 
Remedies  are  best  applied  in  the  form  of  solutions  for  the  reason  that 
all  parts  of  the  animal's  body  are  thus  easily  reached  in  the  dipping 
process.  Hand  dressing  or  scrubbing  or  the  application  of  ointments 
may  be  practiced  where  dipping  is  not  practical,  but  even  so  all  parts 
of  the  animal  should  be  thoroughly  treated. 

Mayo^  of  the  Virginia  Polytechnic  Institute  recommends  a  "lime 

1  Braun,  Max,  1908.  The  Animal  Parasites  of  Man.  (English  Edition.) 
William  Wood  &  Co.  New  York,  xix  +  453  pp. 

2  Mayo,  N.  S.,  1910.  Some  diseases  of  swine.  Bull.  189,  Virginia  Poly. 
Inst.  Agr.  Exp.  Sta.,  19  pp. 


MITES  333 

and  sulphur"  dip  most  highly.  He  uses  8  pounds  of  fresh  lime  and  24 
pounds  of  flowers  of  sulphur  to  100  gallons  of  water,  slaking  the  lime 
with  sufficient  water  to  form  a  thick  paste,  sifting  in  the  sulphur  and 
mixing  with  a  hoe.  This  mixture  is  placed  in  a  kettle  with  25  to  30 
gallons  of  water  and  boiled  for  one  hour  at  least,  two  hours  being  better. 
Mayo  suggests  using  the  entire  mass  for  swine,  which  must  not,  however, 
be  done  for  sheep.  The  dip  is  used  warm  at  a  temperature  of  from 
100°  to  110°  F.  -This  temperature  may  be  maintained  by  running  a 
steam  pipe  along  the  bottom  of  the  dipping  vat. 

Prepared  "lime  and  sulphur"  dips  can  be  secured  readily  on  the 
market,  and  are  commonly  used  at  the  rate  of  one  part  of  the  solution 
to  fifteen  parts  of  water,  however,  care  should  be  exercised  to  use  the 
dip  as  directed,  owing  to  variation  in  constituents.  Coal  tar  dips  are 
also  used  extensively  and  give  good  results  if  used  properly. 

Dipping  vats  may  be  made  of  wood  or  concrete  and  are  usually  set 
in  the  ground  at  a  slight  elevation  to  insure  drainage  away  from  the 
vat.  A  convenient  size  for  a  vat  is  "  ten  feet  long  on  top,  eight  feet 
long  on  the  bottom,  one  foot  wide  on  the  bottom  and  two  feet  wide  at 
the  top.  The  end  where  the  hogs  enter  should  be  perpendicular  and  the 
other  end  inclined,  with  cleats,  so  that  the  hogs  can  emerge  after  passing 
through.  The  entrance  should  be  by  a  slide.  For  pigs  and  small 
shoats  that  can  be  easily  handled,  a  barrel  serves  the  purpose  well ;  the 
pigs  can  be  caught,  plunged  in  the  dip  and  held  there  the  required  time. 
Some  successful  swine  raisers  build  cement  bathing  places  or  wallows 
for  swine  and  keep  these  filled  with  a  watery  solution  of  some  dip  or 
disinfecting  solution.  If  swine  have  wallowing  holes  filled  with  water, 
some  of  the  good  dips  should  be  put  in  these  frequently."  The  time  to 
treat  young  pigs,  and  this  is  important,  is  at  weaning  time.  Dipping 
twice  as  for  older  animals  is  necessary,  and  by  placing  them  in  unin- 
fected quarters  they  ought  to  remain  clean. 

Mangy  swine  should  be  hand  dressed  with  a  stiff  brush  before  dip- 
ping in  order  to  loosen  up  scabs,  and  then  kept  in  the  dip  long  enough  to 
permit  the  solution  to  soak  through  the  scabs,  certainly  not  less  than 
two  minutes.  All  the  animals  must  be  dipped  a  second  time  in  eight 
or  ten  days  in  order  to  destroy  the  mites  which  have  hatched  from  the 
eggs  which  are  not  destroyed. 

Mayo  (1910,  loc.  cit.)  recommends  a  disinfecting  whitewash  to  be 
applied  to  pens,  etc.,  viz.,  "  Fresh  lime,  25  pounds,  flowers  of  sulphur, 
15  pounds,  mix  the  sulphur  with  a  little  water,  to  a  paste,  add  30  gal- 
lons of  water  and  cook  for  an  hour,  then  add  water  sufficient  to  make 
50  gallons  and  apply  with  a  spray  pump,  using  a  '  Bordeaux  '  nozzle." 

Equine  Mange.  —  Sarcoptic  acariasis  in  horses,  mules  and  asses 
is  caused  by  Sarcoptes  scabiei  var.  equi.  This  species  is  also  transmis- 
sible to  man  and  is  said  to  be  the  chief  cause  of  the  itch  of  cavalrymen 
and  others  handling  horses  extensively.  Infestations  on  humans  only 
last  for  two  or  three  weeks. 


334       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

The  most  reliable  diagnostic  character  is  the  discovery  of  the  mite, 
which  is  accomplished  as  in  swine  mange.  The  usual  symptoms  ^ 
are  first  of  all  a  strong  tendency  to  rub  some  circumscribed  part  such  as 
the  head,  root  of  the  mane  or  tail,  withers  or  back,  due  to  an  incessant 
itching.  If  a  person  scratches  the  affected  parts,  the  animal  moves  its 
lips  as  though  it  were  nibbling.  The  skin  of  these  parts  also  shows  an 
eruption  of  "  fine  conical  papillae."  The  hair  here  stands  erect  and  bristly, 
many  having  dropped  out,  but  totally  bare  spots  in  which  there  are  no 
isolated  hairs  apparently  do  not  occur  in  mange,  but  do  in  ringworm 
according  to  Law.  The  affected  parts  are  at  first  scurfy,  then  become 
covered  with  yellowish  scabs,  which  latter  exude  matter  due  to  the 
rubbing  and  inflammation,  and  finally  there  are  formed  scabs  and  crusts, 
often  with  deep  crevices.  During  the  first  fourteen  days  the  progress 
of  the  disease  is  usually  slow,  but  by  the  sixth  week  the  ravages  of 
the  disease  become  extensive  and  there  is  rapid  progress. 

The  life  history  and  habits  of  Sarcoptes  scabiei  var.  equi  correspond 
in  every  respect  with  other  species  already  described. 

Treatment  of  Equine  Mange.  —  Before  applying  a  local  remedy  for 
mange  it  is  necessary  to  clip  the  entire  animal  so  as  to  disclose  all  points 
of  attack  which  might  otherwise  be  hidden  by  hair.  The  clipped 
hair  must  not  be  blown  by  the  wind  and  should  be  burned.  The 
parts  affected  are  next  thoroughly  lathered  and  left  for  a  short  while 
to  soften,  after  which  warm  water  is  applied  and  the  scabs  rubbed  off 
as  far  as  possible  with  wisps  of  hay  or  straw  and  these  also  burned. 
The  affected  parts  are  now  ready  for  a  parasiticide,  which  must  be 
applied  by  hand. 

Many  remedies  may  be  had  for  mange,  all  of  which  have  more  or  less 
virtue,  but  the  writer  has  found  that  those  containing  sulphur  have  the 
greatest  virtue.  The  ordinary  "lime  and  sulphur"  sheep  dips  applied 
locally  and  thoroughly,  repeated  three  or  four  times  at  intervals  of  five 
days,  ordinarily  prove  effective.  Among  other  remedies  Law  (1905, 
loc.  cit.)  recommends  creosote,  5  parts,  alcohol,  5  parts,  water,  25  parts ; 
to  be  rubbed  in  thoroughly  two  or  three  times  at  intervals  of  from  three 
to  five  days.  The  application  of  a  2  per  cent  solution  of  Chloronaph- 
tholeum  applied  as  above  proves  very  satisfactory,  as  does  Kreso  dip, 
one  to  forty. 

Stalls  in  which  mangy  horses  have  been  kept  must  be  disinfected 
with  live  steam  or  boiling  water  or  mercuric  chloride  one  part  to  500  of 
water.  If  the  latter  is  used  its  very  poisonous  properties  must  be 
considered.  Brushes,  scrapers,  rubbers,  etc.  must  be  boiled ;  harness 
must  be  rubbed  thoroughly  with  a  strong  disinfectant,  for  example 
2  per  cent  formaldehyde,  or  Chloronaphtholeum. 

Bovine  Mange.  —  Sarcoptic  acariasis,  or  mange,  in  cattle  is  said  to  be 
rare ;  however,  the  psoroptic  form  (scabies)  is  quite  common. 

1  Law,  James,  1909.  Textbook  of  Veterinary  Medicine.  Vol.  V.,  621  pp. 
Ithaca,  N.Y. 


MITES 


335 


Canine  Mange.  —  Mange  of  dogs  is  caused  primarily  by  Sarcoptes 
scahiei  var.  catiis,  closely  resembling  the  swine  variet}'.  Mange  in  the 
dog  appears  first  on  the  muzzle,  around  the  eyes,  on  ears  and  breast 
and  later  spreads  to  the  back,  abdomen  and  elsewhere.  Symptoms  are 
much  as  in  swine  and  horses.  Canine  mange  is  evidently  transmissible 
to  humans. 

Treatment  for  Canine  Mange.  — -  Long-haired  dogs  must  be  clipped 
before  applying  a  remedy.  Law  recommends  the  following  treatment : 
"  the  whole  skin  may  be  covered  with  a  solution  of  equal  parts  of  green 


Fig.  203.  —  Showing  (a)  normal  leg  and  claw  of  a  fowl   and  (6)  one  affected  with  sar- 
coptic  mites,  Cnemidocoptes  rtiutans,  causing  scaly  leg. 

potash  soap  and  alcohol  and  just  enough  carbolic  acid  to  give  it  the 
odor.  This  is  washed  off  next  day  and  the  surface  is  covered  with  the 
following :  Naphthalin,  ^  oz.,  vaseline,  2  oz.,  or  alcohol  1  pint  makes  a 
most  agreeable,  if  somewhat  expensive,  dressing,  which,  though  slow, 
is  effective.  Creolin,  1  part,  in  alcohol,  15  parts,  is  very  efficient." 
Tobacco,  carbolic  acid  and  other  poisons  which  may  be  licked  off  by 
the  dog  should  not  be  used,  unless  a  tight  muzzle  is  provided. 

Other  Mange  Mites.  —  Mange  of  cats  is  said  to  be  caused  by  Sar- 
coptes minor  var.  jelis,  mange  of  goats  by  Sarcoptes  scahiei  var.  caprce, 
and  of  camels  by  Sarcoptes  scahiei  var.  cameli. 

Scaly  Leg  Mite  of  Poultry.  —  The  legs  of  domestic  fowls  (chickens, 
turkeys,  pheasants,  etc.)  are  frequently  covered  with  heavy  scales  and 
incrustations  (Fig.  203).  This  condition  is  produced  by  a  burrowing 
mite  (Fig.  204),  Cnemidocoptes  (Sarcoptes)  mutans  Robin.     The  mites 


336       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


burrow  and  live  in  the  skin,  depositing  their  eggs  in  these  channels  as 
do  the  mange  mites.  Scaly  leg  is  easily  transmitted  from  fowl  to  fowl, 
hence  the  infested  birds  should  be  isolated  and  treated. 

Treatment  of  "  Scaly  Leg." — -The  legs  must  be  soaked  and  manipu- 
lated with  the  hands  in  soap  and  warm  water  in  order  to  soften  the  scabs. 
Then  when  dry,  "  apply  a  coating  of  balsam  of  Peru,  or  an  ointment 
containing  2  per  cent  of  carbolic  acid  "  or  "a  mixture  of  one  part  of  oil 
of  caraway  with  five  parts  of  vaseline  "  (U.  S.  Dept.  of  Agr.,  Farmers' 
Bull.  530).     The  writer  has  repeatedly  recommended  dipping  the  legs 


Fig.  204.  —  (a)  Photograph  of  a  portion  of  scale  from  a  fowl  affected  with  "scaly  leg," 
showing  mites  {Cnemidocoptes  mutans)  in  situ;  (b)  enlargement  of  an  individual 
mite.     X  170. 

of  the  fowl  in  a  vessel  containing  1  part  kerosene  and  1  part  linseed  oil ; 
the  oil  must  not  touch  the  feathers  on  the  leg  otherwise  the  skin  may 
suffer.  This  dipping  process  is  best  done  while  the  birds  are  roosting, 
lifting  each  bird  from  the  roost,  dipping  and  then  replacing  it.  The 
process  should  be  repeated  in  not  over  a  week. 

Depluming  Mite.  —  Cnemidocoptes  gallinoB  Railliet,  known  as  the 
deplummg  mite,  is  closely  related  to  the  "  scaly  leg  mite,"  but  attacks  the 
skin  of  the  fowl  near  the  base  of  the  feathers.  The  mites  themselves  do 
not  cause  the  bird  to  lose  its  plumage,  but  the  intense  itching  caused 
by  the  mites  impels  the  host  to  pluck  its  feathers  in  an  attempt  to  reduce 
the  itching. 

Dipping  the  birds  in  a  2  per  cent  solution  of  creolin,  or  in  a  2  per 
cent  solution  of  Zenoleum,  or  rubbing  the  skin  with  a  sulphur  ointment 
will,  if  the  treatment  is  repeated,  relieve  the  trouble  considerably. 


MITES  337 

B.   Scab  Mites  —  Psoroptic  Acariasis 
Family  SarcoptidoB 

Characteristics  of  Psoroptic  Mites.  —  The  psoroptic  or  scab  mites 
belong  to  the  family  Sarcoptida'  as  do  the  itch  and  mange  mites,  hence 
partake  of  the  family  characteristics.  However,  in  the  psoroptic  mites 
the  legs  are  long  and  slender,  all  four  pairs  extending  beyond  the  margin 
of  the  body  which  is  elongate  (Fig.  205).  The  "  pedicel  of  the  suckers 
is  jointed  "  and  the  "  mandibles  styliform,  serrate  near  tip  "  and  suited 
for  piercing.     The  psoroptic  mites  do  not  burrow,  as  do  the  sarcoptic 


Fig.  205.  —  Showing  life  history  and  general  characteristics  of  a  typical  psoroptic  or  scab 
mite.  Egg  (lower  left)  ;  larva  (lower  right) ;  male  (upper  right) ;  female  (upper  left). 
Psoroptes  communis  var.  equi  of  the  horse.       X  85. 

mites,  but  live  at  the  base  of  the  hairs  of  the  host,  piercing  the  skin, 
causing  an  exudate  which  partially  hardens,  forming  scabs  which  pile 
up  as  a  crust  of  loose  humid  matter.  This  condition  is  known  as  scabies 
or  scab.  Among  the  piled  up  scabs  are  deposited  the  eggs.  Owing  to 
the  loose  condition  of  the  scabs  and  the  hardihood  of  the  mites,  this 
form  of  acariasis  becomes  quickly  and  easily  distributed  from  animal 
to  animal  by  contact  and  by  rubbing  against  fences,  trees,  and  the  like. 
The  commonest  scab  mites  belong  to  the  genus  Psoroptes  of  which 
Psoroptes  communis  var.  ovis  of  the  sheep  is  best  known.     Other  varieties 


338 


MEDICAL  AND   VETERINARY   ENTOMOLOGY 


of  this  species  infest  cattle  and  horses  mainly.     Several  species  of  psorop- 
tic  mites  attack  the  ears  of  cats  and  dogs,  Otodedes  cygnotls  Gedoclst. 

Ovine  Scabies  (Sheep  Scab)   Psoroptes  communis  var,   ovis    (Fig. 
206)  is  the  causative  organism  of  scabies  in  sheep.     This  is  by  far  the 


Fig.  206. 


Sheep  scab  mite,  Psoroptes  communis  var.  ovis;   male  (left);    female  (right). 
X75. 


most  important  species  of  scab  mite.  However,  with  the  widespread 
use  of  dips,  and  rigid  quarantine  regulations,  scabies  in  sheep  is  grad- 
ually being  controlled. 

The  sheep  scab  mite  is  easily  visible  to  the  naked  eye.  The  adult 
female  measures  about  "one  fortieth"  of  an  inch  in  length  by  "one- 
sixtieth"  of  an  inch  in  breadth,  and  the  male  "one-fiftieth"  by  "one- 
eightieth"  of  an  inch.  As  in  all  psoroptic  species  the  mites  are  found 
on  the  surface  of  the  body  among  the  scabs  at  the  base  of  the  hairs. 

The  parts  of  the  body  most 
thickly  covered  with  wool  are 
chiefly  aftected. 

Symptoms  of  Sheep  Scab. 
—  Scabies  is  first  indicated 
by  a  slight  "tagging"  of  the 
wool,  the  coat  becomes  rough, 
ragged  and  matted  at  the 
points  affected  (Fig.  207). 
Tags  of  wool  are  torn  away 
by  the  sheep  or  are  left  at- 
tached to  rubbing  posts  and 
other  objects  against  which 
_      „^.,       .       ,  ,  the  animal  rubs.    The  sheep 

t  iG.  207.  —  An  advanced  ease  of  sheep  scabies.  .1  •  1  1 

scratches  vigorously  and 
shows  signs  of  intense  itching.  "  The  skin  of  the  affected  part  is  covered 
with  yellowish  papules  of  varying  size,  and  a  marked  accumulation  of 


MITES  339 

scurf  among  the  roots  of  the  wool.  Later  the  affected  skin  swells  uni- 
formly, and  the  increasing  exudation  concretes  into  a  massive  scab  en- 
veloping the  roots  of  the  wool,  so  that  as  it  increases  layer  by  layer  on 
its  deeper  surface,  it  lifts  the  fibers  out  of  their  follicles,  detaching  the 
wool  and  leaving  extensive  bare  scabby  patches.  The  denuded  surface 
shows  all  the  variation  of  lesions  shown  in  other  mangy  animals.  Pap- 
ules, vesicles,  pustules,  scabs,  cracks,  excoriations,  and  even  sloughs 
may  appear  at  different  points.  Sometimes  in  clipped  sheep  the  exudate 
forms  a  uniform,  smooth,  parchment-like  crust  covering  the  whole  ex- 
posed area.  Aroimd  these  bare  patches  the  wool  is  encrusted  at  its  roots, 
or  shows  a  dark,  dirty,  scurfy  layer  composed  of  epidermic  cells,  yolk, 
dried  exudate  and  the  exuvia^  of  the  acarus.  Beneath  this  the  parasite  is 
found  in  myriads.    The  bare  spots  may  show  comparatively  few  "  (Law) . 

Life  History  of  the  Scab  Mite.  —  The  female  scab  mite  deposits 
an  average  of  about  15  (maximum  30)  eggs,  one  at  a  time,  and  the 
period  of  oviposition  often  lasts  several  days,  when  the  female  evi- 
dently dies.  The  eggs  are  either  attached  to  the  wool  near  the  skin 
or  deposited  directly  upon  the  latter.  The  hexapod  larvae  hatch  in 
from  three  to  seven  days,  the  first  molt  taking  place  in  three  or 
four  days  when  the  fourth  pair  of  legs  appears ;  a  second  and  third 
molt  takes  place  within  the  next  four  or  five  days.  Sexual  maturity 
is  evidently  reached  about  the  time  of  the  second  molt.  Although 
there  is  considerable  variation  in  the  length  of  time  elapsing  from  egg 
to  egg,  twelve  to  fourteen  days  is  ordinarily  accepted  as  an  average. 

Treatment  for  Sheep  Scab.  —  Internal  remedies,  such  as  sulphur, 
have  been  found  to  be  unsuccessful  by  the  U.  S.  Department  of  Agri- 
culture. However,  sulphur  applied  externally  in  the  form  of  "  lime  and 
sulphur  "  dip  has  been  used  for  many  years  as  a  successful  remedy. 
Several  kinds  of  dips  with  variations  are  commonly  used  against  sheep 
scab,  among  them,  lime  and  sulphur,  tobacco  and  sulphur,  tobacco,  cresol, 
coal  tar  products,  Chloronaphtholeum,  Kreso,  etc.  If  proprietary  dips 
are  used,  extreme  care  must  be  exercised  in  following  the  directions. 
The  dip  should  have  the  approval  of  the  U.  S.  Department  of  Agricul- 
ture. All  dips  must  be  repeated  in  seven  or  eight  days  and  not  later 
than  ten  days  in  order  to  destroy  the  mites  newdy  hatched  from  eggs,  since 
very  few  dips,  except  perhaps  creosote  dips,  are  injurious  to  the  eggs. 

Lime  and  Sulphur  Dips.  —  Experience  in  many  sheep-raising  dis- 
tricts has  proved  that  lime  and  sulphur  dips  are  most  efficient  in  the 
control  of  scab,  if  properly  used.  Damage  to  the  wool,  if  dipping  is 
done  shortly  after  shearing,  is  very  slight  indeed.  If  there  is  any 
doubt,  or  injury  has  been  produced  in  the  use  of  lime  and  sulphur,  other 
dips  are  available,  notably  nicotine. 

Among  the  varieties  of  lime  and  sulphur  dips  mentioned  by  the  LT.  S. 
Bureau  of  Animal  Industry  ^  are  the  following : 

1  Salmon,  D.  E.,  and  Stiles,  Ch.  WardeU,  1903.  Scab  in  Sheep.  U.  S.  Dept. 
Agr.  Farmers'  Bull.  No.  159,  45  pp. 


340       MEDICAL   AND   VETERINARY  ENTOMOLOGY 

1.  For  fresh  scab   (U.  S.  B.  A.  I.  formula) : 

]                          Flowers  of  sulphur       24  lbs. 

Unslaked  lime 8  lbs. 

Water 100  gals. 

2.  For  very  hard  scab   (Fort  Collins  formula)  : 

Flowers  of  sulphur 33  lbs. 

..'■  Unslaked  lime 11  lbs. 

Water 100  gals. 

3.  For  unusually  severe  cases  (Nevada  formula) : 

Flowers  of  sulphur IGf  lbs. 

Lime 33^  lbs. 

Water 100  gals. 

According  to  the  U.  S.  Bureau  of  Animal  Industry  "  thirty-three 
pounds  of  lime  to  one  hundred  gallons  of  water  is  the  largest  proportion 
admissible  under  any  circumstance." 

How  to  Prepare  Lime  and  Sulphur  Dip.  —  Much  time  may  be  saved 
by  purchasing  the  lime  and  sulphur  already  prepared  and  using  it  as 
directed,  but  the  mixture  may  be  prepared  as  follows,  as  directed  by  the 
United  States  Department  of  x\griculture  : 

^'  A.  Take  8  to  11  pounds  of  unslaked  lime,  place  it  in  a  mortar 
box  or  a  kettle  or  pail  of  some  kind,  and  add  enough  water  to  slake  the 
lime  and  form  a  "  lime  paste  "  or  "  lime  putty." 

Many  persons  prefer  to  slake  the  lime  to  a  powder,  which  is  to  be 
sifted  and  mixed  with  sifted  sulphur.  One  pint  of  water  will  slake  three 
pounds  of  lime,  if  the  slaking  is  performed  slowly  and  carefully.  As  a 
rule,  however,  it  is  necessary  to  use  more  water.  This  method  takes 
more  time  and  requires  more  work  than  the  one  given  above,  and  does 
not  give  any  better  results.  If  the  boiled  solution  is  allowed  to  settle, 
the  ooze  will  be  equally  as  safe. 

"  B.  Sift  into  this  lime  paste  three  times  as  many  pounds  of  flowers 
of  sulphur  as  used  of  lime,  and  stir  the  mixture  well. 

Be  sure  to  weigh  both  the  lime  and  the  sulphur.  Do  not  trust  to 
measuring  them  in  a  bucket  or  to  guessing  at  the  weight. 

"  C.  Place  the  sulphur  lime  paste  in  a  kettle  or  boiler  with  about 
25  or  30  gallons  of  boiling  water,  and  boil  the  mixture  for  two  hours  at 
least,  stirring  the  liquid  and  sediment.  The  boiling  should  be  con- 
tinued until  the  sulphur  disappears,  or  almost  disappears,  from  the  sur- 
face ;  the  solution  is  then  of  a  chocolate  or  liver  color.  The  longer  the 
solution  boils  the  more  the  sulphur  is  dissolved,  and  the  less  caustic  the 
ooze  becomes.  Most  writers  advise  boiling  from  thirty  to  forty  minutes, 
but  the  Bureau  obtains  a  much  better  ooze  by  boiling  from  two  to  three 
hours,  adding  water  when  necessary. 

"  D.  Pour  the  mixture  and  sediment  into  a  tub  or  barrel  placed  near 
the  dipping  vat  and  provided  with  a  bunghole  about  four  inches  from 
the  bottom  and  allow  ample  time  (two  to  three  hours,  or  more  if  neces- 
sary) to  settle. 

The  use  of  some  sort  of  settling  tank  provided  with  a  bunghole  is  an 


MITES  341 

absolute  necessity,  unless  the  boiler  is  so  arranged  that  it  may  be  used 
both  for  boiling  and  settling.  An  ordinary  kerosene  oil  barrel  will 
answer  very  well  as  a  small  settling  tank.  To  insert  a  spigot  about 
three  to  four  inches  from  the  bottom  is  an  easy  matter.  Draining  off 
the  liquid  through  a  spigot  has  the  great  advantage  over  dipping  it  out, 
in  that  less  commotion  occurs  in  the  liquid,  which  therefore  remains 
freer  from  sediment. 

"  E.  When  fully  settled,  draw  off  the  clear  liquid  into  the  dipping  vat 
and  add  enough  warm  water  to  make  100  gallons.  The  sediment  in 
the  barrel  may  then  be  mixed  with  water  and  used  as  a  disinfectant,  but 
under  no  ciraonstcnices  sliould  it  be  used  for  dippimj  purposes.'' 

The  Dipping  Vat.  —  Dipping  vats  may  be  constructed  either  of  wood 
or  of  concrete,  should  be  about  nine  inches  wide  at  the  bottom,  two  feet 
six  inches  at  the  top,  about  5  feet  deep,  and  thirty-five  to  forty  feet  in 
length.  The  entrance  end  is  built  steep  while  the  exit  end  has  a  gradual 
slant  provided  with  cleats. 

How  to  Proceed.  —  The  sheared  sheep  are  driven  into  the  receiving 
pan,  the  dip  having  been  prepared  in  the  meantime  and  warmed  to 
102°  to  105°  F.  One  after  another  the  sheep  are  forced  into  the  dip,  in 
which  they  must  be  kept  two  minutes  and  the  head  drenched  at  least 
once  while  traveling  toward  the  exit  end  of  the  vat  (see  Fig.  208). 
From  the  vat  the  sheep  emerge  in  dripping  pens. 

Tobacco  Dips.  —  Tobacco  (nicotine)  dips  are  now  used  very  exten- 
sively with  excellent  results.  Tobacco  dips  are  used  either  with  or 
without  sulphur.  Owing  to  variation  in  nicotine  content,  homemade 
dips  or  proprietary  tobacco  dips  are  not  safe  unless  the  percentage  is 
ascertained.  When  diluted  ready  for  use  the  nicotine  content  must  he 
.07  of  one  per  cent,  —  a  requirement  of  the  Bureau  of  Animal  Industry. 

After  a  very  careful  and  rigid  experiment  conducted  by  the  Kentucky 
Agricultural  Experiment  Station  ^  in  cooperation  with  the  Bureau  of 
Animal  Industry  with  reference  to  the  addition  of  sulphur,  the  follow- 
ing conclusions  w^ere  reached : 

"  With  the  conditions  under  which  this  experiment  was  carried  on, 
as  given  in  this  bulletin,  the  addition  of  flowers  of  sulphur  in  the  pre- 
scribed dilutions  of  nicotine  did  not,  as  far  as  could  be  discerned,  enhance 
the  value  of  these  dips  in  curing  sheep  of  the  disease  of  scabies. 

After  the  conclusion  of  the  above  experiment,  dippings  were  con- 
ducted by  the  Bureau  of  Animal  Industry  on  the  western  ranges  under 
field  conditions.  The  results  were  confirmatory  to  the  conclusions 
drawn  from  the  above  experiments  and  a  ruling  was  made  by  the  Bureau, 
taking  effect  May  1,  1911,  withdrawing  the  requirement  that  sulphur 
be  added  to  tobacco  dips.  The  ruling  requires  that  seven-hundredths 
of  one  per  cent  of  nicotine  be  used  at  each  dipping." 

1  Good,  Edwin  S.,  and  Bryant,  Thomson  R.,  1911.  The  dipping  of  sheep 
for  scabies  in  tobacco  dips  with  and  without  the  addition  of  flowers  of  sulphur. 
Kentucky  Agr.  Exp.  Sta.  Bull.  157,  pp.  183-193. 


342        MEDICAL  AND   VETERINARY   ENTOMOLOGY 


Fig.  20tS.  —  Dipping  sheep,  (a)  plunging  the  sheep  into  the  vat;  (6)  sheep  swimming 
through  the  vat ;  (c)  sheep  emerging  from  the  vat ;  (d)  entering  the  pens  after  emerg- 
ing from  the  vat.      (Photo  by  G.  P.  Gray.) 


MITES  343 

The  second  dipping  in  the  above  experiment  was  given  in  ten  days 
and  the  temperature  of  the  water  was  105°  F. 

A  tobacco  extract  containing  2.9  per  cent  nicotine  must  (according 
to  the  above  bulletin)  be  diluted  with  56.85  gallons  of  water  to  produce 
.07  per  cent  nicotine  dip,  or  80.14  gallons  of  water  for  a  .05  per  cent  nico- 
tine dip.  Nicotine  sulphate  (about  40  per  cent  nicotine)  must  be 
diluted  with  86.17  gallons  of  water  for  .07  per  cent  nicotine  or  120.70 
gallons  for  a  .05  per  cent  solution. 

If  sulphur  is  used  with  tobacco,  16  pounds  of  flowers  of  sulphur  are 
required  per  100  gallons  of  water.  The  sulphur  is  made  into  a  thin  paste 
with  water  before  adding  it  to  the  dip. 

Other  Dips  Used  for  Sheep  Scab.  —  Great  care  should  be  exercised 
in  selecting  proprietary  sheep  dips ;  many  are  unreliable  and  result  in 
waste  of  money,  time  and  energy.  The  carbolic  acid  dips  vary  consid- 
erably in  their  cresol  content  even  in  packages  sold  under  the  same  label. 
At  all  events  use  the  dip  exactly  as  recommended.  Among  the  more 
widely  used  dips  other  than  those  mentioned  above  are  Kreso,  used 
1  to  72,  Zenoleum,  1  to  50,  and  Chloronaphtholeum,  1  to  50.  The  rat- 
ing of  the  U.  S.  Bureau  of  Animal  Industry  should  govern  the  choice  of 
the  remedy. 

Bovine  Scabies.  —  Scabies  in  cattle  is  caused  by  Psoroptes  communis 
var.  hovis  and  is  comparatively  common.  The  disease  usually  appears 
at  the  root  of  the  tail,  thighs,  neck  and  withers  and  spreads  rapidly  to 
other  parts  of  the  body. 

Treatment  for  scabies  in  cattle  is  most  successfully  undertaken  with 
tobacco  sulphur  dips  or  lime  and  sulphur  dips.  The  former  is  used  as 
in  sheep  scab,  while  in  the  latter  twelve  pounds  of  unslaked  lime  and 
twenty-four  pounds  of  flowers  of  sulphur  to  one  hundred  gallons  of  water 
are  used. 

The  following  general  directions  are  given  by  the  South  Dakota 
Agricultural  Experiment  Station  :  ^ 

"1.  The  temperature  of  the  dipping  vat  should  be  constantly  main- 
tained at  from  103°  F.  to  105°  F. 

"  2.  Animals  badly  affected  are  preferably  to  be  hand  dressed  by 
scrubbing  the  scabby  areas  with  a  stronger  solution  of  the  dip.  When 
lime  and  sulphur  is  used  this  has  the  effect  of  softening  the  firm  scab, 
allowing  the  dip  to  penetrate. 

"  3.  Each  animal  should  be  held  in  the  vat  for  two  minutes,  and 
completely  immersed  twice. 

"  4.  All  animals  that  have  been  in  contact  with  the  diseased  ones 
should  be  regarded  as  infected  and  dipped. 

"  5.  The  dipping  should  be  repeated  in  from  ten  to  fourteen  days  to 
destroy  the  parasites  that  may  have  hatched  out  subsequently  to  the 
first  dipping. 

1  Moore,  E.  L.,  1911.  Scabies  (Mange)  in  Cattle.  Agr.  Exp.  Sta.  South 
Dakota  State  CoUege  of  Agr.  and  Meeh.  Arts,  Bull.  131,  pp.  203-216. 


344       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


"  G.  Dipped  cattle  should  not  be  returned  to  infected  stables  or 
corrals." 

Equine  Scabies.  —  Scabies  of  horses  and  mules  is  traceable  to 
Psuruptes  cumm-unis  var.  equi  (Fig.  205).  This  variety  is  also  known  as 
the  "long-nosed Psoroptes."  Owing  to  the  confluent  sores,  exudate, and 
smooth  surface  where  scabs  have  been  rubbed  off  this  disease  is  also 
known  as  "  humid  mange."  The  mites  are  more  easily  discovered  than 
in  sarcoptic  acariasis,  and  owing  to  the  more  exposed  condition  of  the 
organisms  the  disease  is  easier  of  control. 

Treatment  of  Equine  Scabies  does  not  differ  materially  from  mange. 
Therefore  the  usual  preliminary  treatment  with  soap  and  water  is 
pursued,    followed    with    a    parasiticide.     Law    strongly    recommends 

, 1    Roll's  formula  of  tar  and   sulphur  ^   lb.   each, 

green    soap    and    alcohol,    1    pound    each.     The 
usual  disinfection  of  stalls,  harness,  brushes,  etc., 
^^  must  be  pursued. 

^^^  Mites  in  Ears  of  Rabbits,  Cats  and  Other 

J^^^k  Animals.  —  A   comparatively   common   affection 

^^^^B  of  domesticated  rabbits,  also  of  cats  and  dogs, 

^^^H  is  known  as  otacariasis  or  parasitic  otitis  and  is 

^^^B  traceable  to   Symbiotes    auricularum  Railliet   or 

^H  Otodectes  cygnotis  Gedoelst,  resembling  Psoroptes 

^H  very  closely.     The  mites  literally  swarm  in  the 

^V  ears    of    their    host,    causing   much    discomfort, 

^w  tenderness  of  the  ears,  auricular  catarrh,  loss  of 

r  appetite,  wasting,  torticollis,  etc. 

Cleansing  the  ears  first  with  soapsuds  and 
warm  water,  and  then  applying  a  sulphur  oint- 
ment or  a  10  per  cent  solution  of  tincture  of  iodine 
in  glycerine,  or  a  1  per  cent  solution  of  carbolic 
acid  in  linseed  oil  is  recommended.  The  hutches 
or  kennels  must  be  thoroughly  disinfected  with  a  strong  lime  and  sul- 
phur solution  or  carbolic  acid  to  prevent  further  contagion. 


Fig.  209.  —  A  follicle  mite, 
Demodex  folliculorum. 
X  110. 


C.    Follicle  Mites  —  Follicular  Mange 
Family  Demodecidce 

Characteristics  of  Follicle  Mites.  —  The  Demodecidte  include  very 
minute  (.3-.4  mm.)  mites  with  elongated  transversely  striated  abdomen 
and  possessing  four  pairs  of  "  stubby  "  three-jointed  legs  (Fig.  209). 

The  follicle  mite  {Demodex  folliculorum  Simon)  inhabits  the  hair 
follicles  and  sebaceous  glands  of  men  and  other  mammals  "  causing 
inflammation  of  the  gland  (comedones)  ;  their  agglomeration  in  the 
meibomian  glands  (in  man)  sets  up  inflammation  of  the  margins  of  the 
eyelids"  (Braun).     While  the  follicle  mites  may,  under  certain  condi- 


MITES  345 

tions,  produce  acne-like  conditions,  it  is  hardly  probable  that  many  cases 
of  "  blackhead  "  if  any,  may  be  traceable  to  these  mites.  They  are 
nevertheless  very  common,  —  said  to  occur  in  50  per  cent  of  mankind 
in  all  parts  of  the  world. 

The  variety  found  in  man  is  known  as  Demode.v  folliculoruui  var. 
hominis;  that  of  the  dog  as  Demodex  folliculorum  var.  canis;  of  the 
sheep  var.  ovis;  of  the  ox,  var.  hovis ;  of  swine,  var.  suis,  etc. 

In  most  animals  the  follicle  mites  are  found  in  the  region  of  the 
muzzle  and  the  affection  is  known  as  follicular  mange,  manifested  by  a 
reddish  raw  appearance.  According  to  Banks  (1905,  loc.  cit.)  Demodex 
hovis  Stiles  has  been  recorded  from  hides  of  American  cattle  in  which 
swellings  about  the  size  of  a  pea  were  formed  on  the  skin.  In  these 
swellings  great  numbers  of  the  mites  occurred.  The  value  of  the  hides 
is  said  to  be  lessened  to  a  considerable  degree. 

Owing  to  the  fact  that  the  follicle  mites  occur  so  deeply  in  the  skin, 
treatment  is  made  very  difficult.  Penetrating  materials  are  necessary, 
for  example,  benzine,  1  part,  and  olive  oil,  4  parts,  or  applications  of  tinc- 
ture of  iodine.  Frequent  applications  must  be  made  until  a  cure  has 
been  effected. 

D.    Harvest  Mites  or  Chiggers 

Family   Trombidiidce 

Characteristics.  —  Members  of  the  family  Trombidiidse  are  com- 
monly known  as  "  harvest  mites,"  "jiggers,"  or  "  red  bugs."  In  Mexico 
they  are  known  as  "  TIalsahuate."  According  to  Banks  they  "  are  recog- 
nized by  the  body  being  divided  into  two  portions,  the  anterior  (ceph- 
alothorax)  bearing  the  two  anterior  pairs  of  legs,  the  palpi,  mouth  parts 
and  eyes ;  the  posterior  (abdomen)  is  much  larger  and  bears  the  two 
posterior  pairs  of  legs.  The  mandibles  are  chelate,  at  least  there  is  a 
distinct  jaw  or  curved  spine-like  process.  They  are  always  red  in  color, 
some,  however,  being  much  darker  than  others.  The  body  is  covered 
with  bristles  or  feathered  hairs  according  to  the  species.  The  palpi 
are  five-jointed,  quite  prominent,  often  swollen  in  the  middle,  the  penul- 
timate joint  ending  in  one  or  two  claws,  the  last  joint  (often  clavate) 
appearing  as  an  appendage  or  "  thumb  "  to  the  preceding  joint.  The 
legs  are  seven-jointed  ;  the  tarsi  terminate  in  two  small  claws.  The 
legs  are  clothed  in  the  same  manner  as  the  body.  There  are  two  eyes 
upon  each  side  of  the  cephalothorax,  quite  frequently  borne  on  a  distinct 
pedicel." 

The  most  important  genus  aft'ecting  man  is  Trombidium,  of  which 
the  larval  form  is  known  as  Leptus  (Fig.  210),  e.g.  Leptus  autumnalis 
Shaw.  Among  the  species  of  Trombidium  are  T.  Jiolosericeuvi  Say, 
T.  magnificum,  Lee,  etc. 

Habits  and  Life  History.  —  In  the  free-living  adult  stage  the  Trom- 
bidiidae  feed  on  insects  and  do  not  attack  warm-blooded  animals ;    the 


346        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

newly  emerged  larvae  at  once  become  parasitic  on  grasshoppers  and 
other  insects,  where  they  become  full  grown,  molt  and  mature.  In  this 
stage  (the  larval)  the  mites  also  attack  humans  and  other  warm-blooded 
animals,  but  perish  in  the  act  of  burrowing  into  the  skin.  Owing  to  the 
fact  that  the  mites  are  so  abundant  during  the  autumn  they  are  com- 
monly called  "  harvest  mites."  Their  chief  habitat  is  among  the  weeds 
and  tall  grass  in  neglected  pastures,  among  blackberry  bushes  and  the 
like.     The  individuals  which  succeed  in  reaching  maturity  overwinter 

and  deposit  large  numbers  of  eggs  on 
the  ground  in  sheltered  weedy  spots; 
these  hatch  in  summer  and  autumn. 
There  seems  to  be  but  one  generation 
a  year. 

During  midsummer  and  autumn 
it  is  almost  impossible  to  traverse  a 
mite-infested  pasture  without  suffering 
an  attack  of  intense  itching  about  the 
ankles  and  up  to  the  knees  within  a 
few  hours.  The  mites  are  believed 
to  enter  the  skin  either  through  the 
Fig.  210.  —  Chigger  mite  or  harvest  pores,  hair  folliclcs,  or  evcn  directly, 
mite ;  —  larva  (Leptus)  of  Trombi-    There  are  formed  red  blotches  often 

of  considerable  size  and  the  itching  is 
just  about  unbearable.  Water  blisters  of  larger  or  smaller  size  (1  to 
5  mm.  and  over)  appear  in  a  day  or  two  after  itching  begins. 

Treatment  for  Harvest  Mites.  —  The  extreme  irritation  occasioned 
by  these  mites  may  be  relieved  considerably  by  bathing,  using  soap 
freely,  followed  by  sponging  with  a  weak  solution  of  carbolic  acid  (an 
ounce  to  a  quart  of  water),  weak  ammonia,  soda  solution,  or  alcohol, 
or  anointing  the  affected  spots  with  an  ointment  or  salve  containing 
sulphur.  Rubbing  the  skin  with  tobacco  water,  benzine,  kerosene,  or 
glycerine  is  also  suggested  as  a  remedy,  also  as  a  preventative  to  persons 
finding  it  necessary  to  work  in  regions  when  the  jiggers  or  red  bugs  are 
in  season.  Clearing  infested  spots  of  weeds,  shrubbery,  and  tall  grass 
is  necessary  to  control  the  mites. 

E.   The  Poultry  Mite 
Family  GamasidcB 

Gamasid  Mites.  —  The  family  Gamasidae  includes  a  large  number 
of  species  parasitic  mainly  on  birds  and  insects.  The  group  is  some- 
times elevated  to  the  rank  of  a  superfamily  (Gamasoidea)  and  then 
includes  three  families,  viz.,  Dermanyssidfe,  Gamasidse  and  Uropodidse. 
The  close  structural  relationship  of  at  least  the  first  two  hardly  justifies 
this  separation. 


MITES 


347 


From  our  viewpoint  the  most  important  member  of  the  family  Gama- 
sidffi  (or  Dermanyssidse)  is  the  poultry  mite,  Dermanyssus  galUnce  Redi 
(Fig.  211). 

Damage  Done. — The  poultry  mite  is  one  of  the  worst  enemies  of  the 
poultry  raiser  in  the  Southern  states  and  in  California,  and  is  evidently 
a  serious  pest  in  many  other  parts  of  the  world.  The  damage  which 
this  mite  produces  is  very  considerable  and  may  be  summarized  as 
follows :  egg  production  is  greatly  reduced  or  entirely  prevented  as 
shown  by  Uepp  ^ ;  sitting  hens  are  often  caused  to  leave  their  nests  or 
perish ;  newly  hatched  chicks  perish  in 
great  numbers  in  the  presence  of  these 
mites  ;  chickens  lose  flesh,  are  unthrifty, 
and  are  unprofitable  for  marketing ;  loss 
of  blood  and  reduced  vitality  produce 
birds  easily  susceptible  to  disease. 

Habits  and  Life  History.  —  In  size 
the  mites  vary  from  .6  to  .7  mm.  in  length, 
are  somewhat  pear-shaped  and  are  light 
gray  w^hen  unengorged  and  from  light  to 
a  dark  red  when  engorged. 

During  the  daytime  the  mites  remain 
hidden  in  the  crevices  of  the  henhouse, 
under  the  roosts,  under  boards,  etc.  In 
these  hiding  places  the  eggs  are  deposited. 
At  night  the  little  pests  swarm  out  from 
their  hiding  places  and  attack  the  fowls 
upon  the  roosts.  Their  attack  on  the 
fowls  is,  however,  not  restricted  alto- 
gether to  the  night,  but  swarms  of  them 
may  be  found  on  sitting  hens  and  lay- 
ing hens  during  the  day  while  nesting  in 
darker  situations. 

Myriads  of  tiny  eggs  are  deposited  in  all  sorts  of  crevices.  The  six- 
legged  larvse  hatch  in  four  to  six  days,  feed  largely  on  filth  at  first  and 
later  attack  the  chickens,  as  do  the  adults.  Full  growth  is  reached  in 
from  three  to  six  weeks,  depending  on  temperature.  Some  authors  give 
the  time  for  development  at  from  ten  days  to  two  weeks.  There  are 
three  or  four  molts  before  sexual  maturity  is  reached. 

Control  of  the  Poultry  Mite.  —  Above  all  things  extreme  cleanliness 
and  plenty  of  sunlight  are  necessary  to  prevent  rapid  multiplication. 
Kerosene  emulsion  (one  part  to  ten  parts  of  water)  applied  with  a  spray 
pump  to  all  parts  of  the  henhouse,  particularly  the  crevices,  has  been 
found  most  serviceable  in  destroying  the  mites.  The  spray  must  be 
repeated  in  about  five  or  six  days  to  kill  the  mites  hatching  from  the  eggs, 
which  latter  are  not  injured  by  the  spray. 


Fig.  211.  —  The  poultry  mite,  Der- 
manyssus gallince.       X  45. 


iRepp.    John    J.,    1903. 
Sta.  BuU.  69,  pp.  287-294. 


The  chicken  mite.     Iowa    State    College    Exp. 


348       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

It  is  well  to  ^emo^'e  all  roosts  and  paint  these  with  kerosene  or  gaso- 
line, daubing  the  ends  abundantly  with  tar  or  crude  oil  before  replacing. 

Straight  kerosene  applied  with  a  spray  pump  as  directed  for  the 
chicken  tick  proves  very  effective,  if  repeated  two  or  three  times  at  inter- 
vals of  five  or  six  days. 


F.   Louse-like  Mites 
Family   Tarsonemidce 

Characteristics  of  Tarsonemidae.  —  This  is  a  small  family  of  soft- 
bodied  mites  having  in  the  female  a  characteristic  "  prominent  clavate 
organ  of  uncertain  use  "  between  the  first  and  second  pairs  of  legs 
(Fig.  212).  The  third  and  fourth  pairs  of  legs  are  separated  from  the 
first  and  second  pairs  by  a  long  interspace.  There  is  present  a  consid- 
erable sexual  dimorphism  in  the  several  species.  The  piercing,  sucking 
mouth  parts  are  provided  with  slender  needle-like 
stylets.    Many  of  the  species  are  predaceous  or  para- 

isitic,  while  others  suck  the  juices  of  certain  plants. 
Pediculoides  ventricosus  Newport  is  a  widely  dis- 
tributed predaceous  mite  which  attacks  the  larvae  of 
a  number  of  species  of  insects  such  as  the  Angou- 
mois  grain  moth  {Sitotroga  cerealella  Oliv.),  the  wheat 
joint-worm  (Isosoma  tritici  Fitch),  the  peach  twig 
borer  (Anarsia  lineateUa  Zell.),  the  cotton-boll  weevil 
{Antlumom.us  grandis  Boh.),  etc.  It  is  therefore 
normally  a  beneficial  mite,  but  unfortunately  it 
also  attacks  man,  producing  a  very  disagreeable 
dermatitis. 

While  the  male  mite  is  very  tiny,  just  about 
visible  to  the  naked  eye,  the  female  when  pregnant 
becomes  enormously  swollen,  measuring  nearly  a  millimeter  in  length, 
the  abdomen  presenting  a  globular  appearance,  the  cephalothorax  and 
appendages  barely  visible. 

Within  the  enlarged  abdomen  of  the  female  may  be  found  rather 
large  eggs  which  hatch  internally,  and  the  young  mites  develop  to 
maturity  within  the  body  of  the  mother  before  being  extruded.  The 
number  of  young  produced  by  the  female  is  said  to  range  from  a  few  to 
nearly  300. 

A  number  of  epidemics  of  dermatitis  have  been  traced  to  these  mites, 
infection  having  been  brought  about  by  sleeping  on  straw  mattresses 
or  while  laboring  in  grain  fields  at  harvest  time.  The  infection  has  been 
confounded  with  hives,  scabies  and  even  chicken  pox  and  smallpox, 
and  appears  on  the  neck,  chest,  abdomen,  back,  arms,  and  legs,  in  fact 
the  whole  body  may  be  involved  and  the  itching  is  very  intense.  The 
eruption  is  commonly  accompanied  with  fever  as  high  as  102°  F. 


Fig.  212.  — A  louse- 
like mite,  Pedicu- 
loides ventricosus. 
X32. 


MITES 


349 


According  to  Goldberger  and  Schamberg  ^  the  itching  subsides  under 
continuous  exposure  in  from  3  to  7  weeks.  They  also  recommend  treat- 
ing the  affection  with  an  ointment  of  beta  naphthol,  sulphur,  benzoate 
and  lard. 

To  destroy  mites  in  the  straw  of  mattresses  or  in  other  situations, 
fumigation  with  sulphur  or  formaldehyde  gas  or  steaming  is  recom- 
mended. 

As  to  prevention  Webster  ^  suggests  burning  the  grain  stubble  dur- 
ing the  fall,  winter  or  spring,  also  that  threshing  direct  from  the  shock 
resulted  in  the  control  of  the  grain  moth  and  consequently  of  the  para- 
sitic mites. 


G.  Flour  and  Meal  Mites  —  Grocer's  Itch 
Family  Tyrogliyhidoe 

Characteristics  of  Tyrogliphidae.  —  This  family  includes  a  small 
group  of  very  tiny  mites,  ordinarily  about  0.5  mm.  or  less  in  length. 
Several  of  the  species  attack  grain, 
flour,  meal,  dried  meat,  hams,  dried 
fruits,  insect  collections,  etc.  Their 
development  is  so  rapid  that  there 
may  be  literally  millions  of  them  in 
some  stored  products  in  a  few  days. 

The  metamorphosis  of  this  group 
involves  a  peculiar  stage  known  as 
the  Hypo  pus,  appearing  after  the  lar- 
val and  nymphal  stages,  very  unlike 
either  of  these  and  very  different 
from  the  adult.  This  stage  is  said  to 
attach  itself,  non-parasitically,  to 
flies  and  other  insects,  which  serve 
as  disseminators  of  the  mites. 

Persons  handling  stored  products, 
cereals,  flour,  meal,  etc.  may  be  at- 
tacked   temporarily    by    the    mites, 
causing  severe  itching  and  irritation  of  the  skin,  known  as  "  grocer's 
itch." 

Tyroglyphus  siro  Linn,  is  the  cheese  mite,  also  found  in  grain  and 
stored  products;  T.fariiKS  DeG.  (Fig.  213)  is  known  as  the  flour  mite 
but  is  probably  the  same  as  the  former. 


Fig.  213.  — A  stored  food  mite  or  flour 
mite,  Aleurobius  (Tyroglyphus)  farince 
(male).      X  145. 


1  Goldberger,  J.,  and  Schamberg,  .J.  F.,  1909.  Epidemic  of  an  articariod 
dermatitis  due  to  a  small  mite  (Pediculoides  ventricosus)  in  the  straw  of  mat- 
tresses.    U.  S.  Public  Health  Reports,  Vol.  24,  No.  28,  pp.  97.3-97.5. 

2  Webster,  F.  M.,  1910.  A  predaceous  mite  proves  noxious  to  man. 
U.  S.  Dept  of  Agr.  Bu.  of  Ento.  Circ.  No.  118,  24  pp. 


350        MEDICAL  AND   VETERINARY  ENTOMOLOGY 

No  doubt  the  best  way  to  destroy  mites  occurring  in  stored  products 
is  to  subject  them  to  a  dry  heat  of  125°  F.,  or  by  fumigation  with  sulphur 
or  carbon  dioxide. 

H.  Red  Spiders 
Family  Tetranychidce 

Characteristics  of  Tetranychidae. — To  this  family  belong  the  "web- 
spinning  mites,"  most  commonly  infesting  vegetation  and  destructive 
to  fruit  trees  and  other  plants.  The  term  "red  spiders"  is  ordinarily 
applied  to  the  group.  Tetranychus  bimaculatus  Harvey  attacks  many 
species  of  plants  and  is  very  injurious  to  hops. 

Persons  employed  in  picking  hops  and  harvesting  almonds,  etc., 
often  complain  of  itching  produced  by  the  red  spiders,  but  this  soon 
disappears. 


CHAPTER   XX 
VENOMOUS  INSECTS   AND  ARACHNIDS 

Insect  Venoms.  —  Insect  venoms,  like  other  animal  venoms,  are 
toxic  principles  probably  not  greatly  unlike  the  bacterial  toxins,  but 
about  which  we  know  comparatively  little.  Unlike  the  bacterial  toxins 
which  reach  injurious  amounts  after  a  period  of  incubation  subsequent 
to  the  introduction  of  the  corresponding  bacteria  into  the  body,  the 
venoms  on  the  contrary  act  almost  instantly,  i.e.  as  soon  as  introduced. 

The  venoms  act  in  one  or  more  ways  when  introduced  into  the  body, 
1st,  they  may  act  directly  as  solvents  on  the  blood  corpuscles  {hcBino- 
lytic) ;  2d,  they  may  act  directly  on  the  nervous  system  producing  a 
shock  or  inhibiting  reflexes  {neurotoxic)  ;  3d,  producing  an  infiltration 
and  congestion  of  blood  (hcenwrrhagic)  often  in  the  vicinity  of  the  wound 
or  deeper  tissue,  such  as  the  mesenteries,  etc.  A  given  specific  venom 
may  produce  one  or  more  of  the  above  conditions. 

As  has  been  discovered  by  various  investigators  and  as  is  a  matter  of 
common  observation,  repeated  inoculation  of  minute  or  attenuated 
quantities  of  a  venom  may  lead  to  immunity,  so  also  with  venoms  or 
poisons  of  bees,  bedbugs,  mosquitoes,  fleas,  cone-noses,  etc. 

In  the  ants,  bees  and  wasps  (aculeate  hymenoptera)  there  are 
two  poison-secreting  glands,  one  of  which  produces  formic  acid  and  the 
other  an  alkaline  fluid.  The  combination  of  the  two  agents  in  certain 
proportions  is  evidently  necessary  to  produce  the  reaction  of  a  bee  sting. 

The  scorpion  (an  Arachnid)  secretes  a  large  quantity  of  colorless 
acid-reacting  liquid  soluble  in  water  and  heavier  than  the  same.  Ac- 
cording to  Calmette,  less  than  0.0005  gm.  will  kill  a  white  mouse  in  about 
two  hours. 

How  the  Venom  is  Introduced.  —  Venoms  of  insects  in  a  broad  sense 
are  introduced  into  the  bodies  of  animals  in  one  of  three  ways :  1st,  by 
contact,  e.g.  irritating  hairs  of  certain  caterpillars,  such  as  the  brown-tail 
moth  {FAiyroctis  chrysorrhoea  Linn.),  producing  a  condition  similar  to 
nettling,  or  the  vesicating  fluids  of  the  blister  beetles  (Meloidfe),  par- 
ticularly Lytta  vesicatoria  Linn. ;  2d,  by  the  hite  or  thrust  of  a  piercing 
proboscis,  as  in  the  cone-noses  (Reduviidse),  or  pierce  of  the  chelicerse 
of  spiders ;  3d,  by  the  sting,  as  in  the  bees  or  wasps  (aculeate  Hymen- 
optera) and  the  scorpion.  The  operation  and  structure  of  stings  varies 
considerably,  notably  in  the  examples  cited. 

Irritating  or  Nettling  Hairs.  —  A  rash  known  as  the  "  brown-tail 
rash  "  is  traceable  to  the  caterpillar  of  the  brown-tail  moth  {Euyroctis 

351 


352       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

chrysorrhcea  Linn.),  a  common  and  very  destructive  shade  tree  pest  in 
Europe  and  in  America,  especially  New  England.  When  the  cater- 
pillars of  this  species  molt,  myriads  of  tiny  barbed  hairs  are  shed  with 
the  skin.  When  dry  these  hairs  are  blown  about  by  the  wind  and 
coming  in  contact  with  the  skin  of  the  face  or  hands  produce  a  very 
severe  dermatitis.  The  hairs  are  hollow  and  it  has  been  shown  by  Tyzzer 
that  they  contain  a  definite  poisonous  principle  which  is  injected  into 
the  circulation  by  the  sharp-pointed  hair  in  contact  with  the  skin,  thus 
producing  the  rash. 

Blister  Beetles.  —  Blister  beetles  belong  to  the  family  Meloidse 
(=  Cantharidae)  (Order  Coleoptera)  and  are  so  designated  because  of 
their  vesicating  properties,  i.e.  the  application  of  the  pulverized  bodies  of 
many  species,  if  not  all,  produces  a  blistering  of  the  skin.  The  most 
notable  example  of  the  Meloidse  is  the  Spanish  fly,  Lytta  vesicatoria 
Linn,  (see  Chap.  VI). 

The  Meloidfe  (=  Cantharidse)  are  described  by  Comstock,  viz., 
"  The  blister  beetles  are  of  medium  or  large  size.  The  body  is  compara- 
tively soft ;  the  head  is  broad,  vertical  and  abruptly  narrowed  into  a 
neck ;  the  prothorax  is  narrower  than  the  wing  covers,  which  are  soft 
and  flexible ;  the  legs  are  long  and  slender ;  the  hind  tarsi  are  four- 
jointed,  and  the  fore  and  middle  tarsi  are  five-jointed." 

The  blister  beetles  deposit  their  eggs  on  the  ground,  the  larvae  are 
active  and  feed  it  is  said  in  some  species  on  the  eggs  of  locusts  and  soli- 
tary bees,  others  are  predaceous.  They  undergo  a  number  of  changes 
not  usual  to  insects  and  their  development  is  consequently  termed 
hypermetamorphosis.     The  adults  are  vegetable-feeding. 

Venomous  Insects 

Cone-noses  or  Kissing  Bugs,  belonging  to  the  Fam.  Reduviidse  (see 
Chap.  VIII),  are  most  commonly  concerned  with  the  more  painful 
"  bites  "  inflicted  by  insects.  Their  mouth  parts  (see  Chap.  IV)  are 
beautifully  adapted  to  piercing  the  skin  or  covering  of  the  host.  The 
Reduviids  are  essentially  predaceous,  attacking  many  species  of  insects, 
particularly  plant  lice  and  other  soft-bodied  forms  from  which  they  suck 
the  body  fluids.  Attack  upon  humans  is  made  principally,  if  not  wholly, 
in  self-defense.  Persons  picking  up  boards,  sticks  or  stones,  etc.,  may 
accidentally  also  pick  up  one  of  these  insects,  or  in  plucking  a  leaf  or 
flower  from  a  tree  or  other  plant  the  fingers  may  close  upon  the  insect 
as  well,  with  the  result  that  a  very  painful  bite  is  almost  invariably 
inflicted. 

The  principal  offenders  are  about  18-20  mm.  in  length  and  all  bear 
a  general  resemblance  to  the  illustration  (Fig.  214).  Among  the  impor- 
tant species  in  their  relation  to  human  comfort  are  the  following : 
Opsicoetes  (Reduvius)  personatus  Linn.,  known  as  the  "kissing  bug"; 
Conorhinus  sanguisuga  Lee,  the  "  blood-sucking  cone-nose  "  or  "  big  bed- 


VENOMOUS  INSECTS  AND  ARACHNIDS 


353 


bug  "  ;  Conorhinus  protractus  Uhler,  the  "  China  bedbug  "  ;  and  Rasahus 
biguttatus  Say,  the  "two-spotted  corsair." 

The  symptoms  produced  by  Conorhinus  lirotr actus,  the  usual  culprit 
in  California,  are  described  as  follows :  "  In  a  few  minutes  after  a  bite 
the  patient  develops  nausea,  flushed  face, 
palpitation  of  the  heart,  rapid  breathing, 
rapid  pulse,  followed  by  profuse  urticaria  all 
over  the  body.  The  symptoms  vary  with  in- 
dividuals in  their  intensity." 

The  symptoms  described  for  Rasahus 
biguttatus  are  as  follows :  "  Next  day  the  in- 
jured part  shows  a  local  cellulitis  with  a 
central  spot ;  around  this  spot  there  fre- 
quently appears  a  bulbous  vesicle  about  the 
size  of  a  ten-cent  piece  and  filled  with  a  dark 
grumous  fluid ;  a  smaller  ulcer  forms  under- 
neath the  vesicle,  the  necrotic  area  being 
generally  limited  to  the  central  part,  while  the 
surrounding  tissues  are  more  or  less  sw^ollen  and  somewhat  painful." 

Treatment  for  Cone-nose  Bites  is  discussed  in  a  previous  chapter 
(Chap.  VIII). 

Bedbugs  (Fam.  Acanthiidse  =  Cimicidse),  Fleas  (order  Siphonap- 
tera)  and  Mosquitoes  (Fam.  Culicidse),  all  inflict  bites  of  greater  or  less 
severity,  depending  on  individual  cases.  To  many  persons  the  bite  of  any 
one  of  the  above  proves  benign,  while  to  others  even  one  bite  may  prove 
very  irritating.  Frequently  the  severity  of  a  bite  is  traceable  to  an  infec- 
tion induced  by  undue  scratching  with  the  finger  nails.  Ordinarily  the 
itching  may  be  relieved  by  the  application  of  ammonia.  For  a  discussion 
of  each  of  the  groups  the  reader  is  referred  to  the  respective  chapters 
dealing  with  the  same. 


Fig.  214.  — A  typical  blood- 
sucking cone-nose,  Cono- 
rhinus protractus.       X  2. 


The  Bee  Sting  —  Structure  and  Operation 

The  Bee  Sting.  —  For  precision  exhibited  in  minute  parts  and  for 
accuracy  of  operation,  the  sting  of  the  honeybee  {^ipis  meUifera  Linn.) 
stands  unsurpassed  among  the  weapons  of  defense  and  offense  carried 
by  insects.  From  the  barefoot  boy  that  plays  in  the  flower-dotted 
meadow,  to  the  philosopher  delving  in  the  mysteries  of  a  locust  blossom 
at  close  hand,  the  sting  of  the  bee  demands  instant  respect.  Cheshire 
has  nicely  stated  the  matter  thus  :  "Man  and  bees  alike  live  in  a  world 
where  good  and  evil  grow  together,  where  the  thrift  of  the  industrious 
excite  the  cupidity  of  the  idle.  Let  us  then,  accepting  the  sting  with- 
out regret,  strive  to  learn  the  wav  in  which,  for  us,  it  shall  cease  to  be  an 
evil." 

The  following  account  of  the  morphology  and  operation  of  the  bee 
sting  has  been  prepared  by  Miss  Edwina  Fay  Frisbie  and  is  an  extract 


354       MEDICAL  AND   VETERINARY   ENTOMOLOGY 


from  a  thesis  on  this  subject  prepared  under   the   direction   of   the 
writer. 

Morphology  of  Sting.  —  Accepting  the  sting  as  a  speciahzed  ovi- 
positor the  worker  bee,  or  aborted  female,  is  used.  The  sting  can  be 
easily  extracted  either  by  separating  the  segments  of  the  abdomen  from 
it  by  means  of  dissecting  needles,  or  by  squeezing  the  live  bee  between 
forceps,  which  pressure  causes  it  to  protrude  the  sting.     The  sting  can 

then  be  grasped  with 
other  forceps  and 
drawn  out.  After  ex- 
traction, the  sting  can 
be  best  examined 
when  the  parts  are 
floated  out  in  a  few 
drops  of  glycerine. 
For  purposes  of  de- 
scription the  sting 
may  be  divided  into 
three  parts,  viz.  :  the 
piercing  apparatus ; 
the  lateral  plate  and 
appendages ;  the  poi- 
son sac  and  glands. 

The  piercing  ap- 
paratus itself  consists 
of  three  parts,  one  the 
so-called  sheath,  the 
other  two  lying  within 
the  sheath,  and  par- 
tially surrounded  by 
it.  In  appearance  the 
sheath  is  yellowish 
and  translucent.  The 
darts,  which  present 
concave  surfaces  to 
one  another,  are 
highly  chitinous.  The 
distal  one  third  of  the 
dart  possesses  a  series 
of  sharp  barbs,  whose  shape  has  been  aptly  compared  to  the  tip  of  a 
crochet  needle.  Cheshire  states  that  each  dart  has  from  three  to  six 
barbs,  other  writers  seem  doubtful  as  to  the  number.  The  careful 
observations  of  the  writer  in  which  many  barbs  have  been  examined 
give  no  instance  in  which  it  was  impossible  to  distinguish  ten  barbs 
on  the  outer  edge  of  each  dart  (Fig.  215).  Several  writers  state  that 
poison  pores  are  to  be  found  at  the  base  of  each  barb,  from  which 


Fig.  215.  —  Sting  of  a  honeybee  {Apis  mellifera).  'a,  the 
two  serrated  darts ;  b,b',  sting  palpi ;  c,  venom  (poison) 
sac ;  d,  venom  gland ;  e,  e',  triangular  plates  or  levers ; 
/,  /',  semilunar  plates  or  levers ;  g,  g',  lateral  plates  or 
levers ;  h,  h',  ^/-shaped  darts ;  i,  i',  points  of  attachment 
for  darts  to  levers  ;  e,  e';  j,  j',  points  around  which  levers 
rotate ;  k,  k',  points  of  attachment  for  levers/,/',    x  17.5. 


VENOMOUS   INSECTS  AND  ARACHNIDS  355 

poison  exudes.  In  this  matter,  experience  forces  the  writer  to  agree 
with  Snodgrass  in  his  remark  that  thus  far  he  has  failed  to  observe  the 
exit  of  poison  elsewhere  than  between  the  darts  at  their  tip. 

Proceeding  upward  on  the  dart  from  the  tiny  barbs,  the  darts  are 
seen  to  form  a  figure  Y  as  they  lie  within  the  sheath.  The  arms  of  the 
Y  gradually  bend  laterally.  The  plates  attached  to  the  upper  edges 
of  these  laterally  bent  arms  will  be  described  under  the  next  heading. 
One  of  the  most  remarkable  portions  of  the  darts  is  the  poison  valve 
with  which  each  is  provided.  At  the  point  of  separation,  the  darts 
each  present  a  delicate  cup-shaped  valve,  whose  closed  portion  is  directed 
downward  toward  the  tip  of  the  sting.  This  is  formed  of  the  same 
chitinous  material  which  composes  the  darts,  and  each  is  free  to  move 
with  the  movement  of  the  dart.  In  order  to  accommodate  this  enlarge- 
ment of  the  darts,  the  sheath  at  this  point  expands  to  about  five  times 
its  smallest  diameter,  which  is  at  the  tip  of  the  sting.  For  at  least  one 
third  of  its  length  the  sheath  at  this  portion  is  expanded  into  a  sym- 
metrical oblong  body  providing  ample  room  for  the  movement  of  the 
darts  and  valves  within. 

A  curious  structure,  said  by  many  writers  to  be  found  on  the  sheath, 
consists  of  two  delicate,  but  strong,  chitinous  tracks  or  guide  rails  on 
which  the  darts,  correspondingly  grooved,  fit  and  move  back  and  forth. 
Since  the  sheath  does  not  sufficiently  surround  the  darts  to  direct  their 
course,  this  guide-rail  system  which  Carlet  has  observed,  and  which  is 
accepted  by  other  authors,  offers  a  pretty  and  probable  solution  of  the 
reason  for  the  smooth  and  accurate  play  of  the  darts  within  the  sheath. 

Lateral  Appendages.  —  The  lateral  appendages  are  of  three  kinds, 
viz.  :  semilunar,  triangular  and  lateral,  according  to  shape  or  posi- 
tion. Both  the  semilunar  and  triangular  plates  are  attached  to  the 
bent  ends  of  the  Y-shaped  darts.  The  triangular  plates  are  attached 
to  the  arms  of  the  darts  almost  at  their  extremities,  while  the  semilunar 
ones  are  connected  for  about  one  third  of  the  distance  from  the  ends 
of  the  arms.  Permitting  this  comparison  of  the  smallest  of  the  plates 
to  a  triangle,  although  the  comparison  is  not  an  exact  one,  the  expla- 
nation of  its  position  may  be  continued  by  saying  that  the  apex  of  the 
triangle  is  that  portion  which  is  attached  to  the  extremity  of  the  dart. 
The  other  two  points  then  point  outward  and  downward,  and  serve  as 
points  of  attachment  for  two  elevated  edges  on  the  lateral  plates  which 
hang  thus  suspended.  As  they  hang,  half  of  their  surface  lies  above 
and  covers  the  dorsal  surface  of  the  semilunar  plates  just  beneath  them. 
Continuing  in  the  same  straight  line  with  the  semilunar  plates  and 
attached  at  their  extremity  to  them,  lie  the  fleshy  palpi  covered  with 
delicate  hairs.  This  outline  description  of  the  position  and  attachment 
of  movable  plates  will  be  supplemented  in  the  explanation  of  their  mech- 
anism, where  they  can  be  more  readily  understood  through  their  function. 

Venom  Sac  and  Glands.  —  The  third  portion  which  completes  the 
structure  of  the  sting  is  the  venom  sac  and  glands.     In  order  to  under- 

2a 


356       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

stand  these,  it  is  necessary  to  know  that  Hymenoptera  are  divided  into 
those  which  kill  their  prey  by  stinging,  and  those  which  only  paralyze 
them.  The  former  are  the  most  complicated  for  they  possess  two 
poison  glands.  One,  the  formic  acid  gland,  which  opens  directly  into 
the  great  poison  sac,  is  the  larger  of  the  two.  The  other,  the  alkaline 
gland,  which  is  comparatively  small,  is  situated  at  the  base  of  the 
poison  sac.  It  is  the  combination  of  the  formic  acid  and  alkaline  sub- 
stances from  the  two  glands  that  results  in  the  death  of  the  attacked 
insect,  or  that  causes  the  extreme  irritation  in  humans. 

The  formic  acid  gland  alone  is  found  in  the  Hymenoptera,  which 
only  paralyze  their  prey  when  stinging  them.  This  fact  has  led  various 
observers  to  make  chemical  tests  of  both  the  formic  acid  and  alkaline 
substance.  The  result,  according  to  Carlet  and  others  has  been  to 
show  that  neither  substance  by  itself  is  effective  except  to  paralyze, 
but  when  combined  the  substances  have  deadly  effects  upon  other  in- 
sects. Carlet's  experiments  to  prove  this  were  made  upon  house  flies 
and  blow  flies  by  injecting  each  substance  singly  and  then  introducing 
both  into  the  body  of  a  fly.     The  results  are  entirely  convincing. 

Operation  of  the  Sting.  —  After  considering  the  very  complicated 
structure  of  this  minute  instrument  of  attack  and  defense  it  will  not  be 
surprising  to  find,  perhaps,  that  the  mechanism  of  its  parts  is  even  more 
complicated  and  at  the  same  time  so  wonderfully  accurate  that  human 
invention  can  only  look  and  marvel. 

The  microscopic  structure  of  parts  makes  an  examination  of  the 
mechanism  extremely  difficult.  Also  the  stubbornness  which  charac- 
terizes a  bee  when  it  would  be  persuaded  to  sting  without  the  usual 
incentive,  adds  to  the  problem  of  studying  the  operation  of  the  sting. 
An  effort  was  made  to  see  the  sting  in  operation  by  confining  a  bee  on 
its  dorsal  side  and  then  prodding  it  until  its  sting  was  angrily  thrust 
in  and  out.  This  process  showed  three  things,  viz.  :  that  the  sharp- 
pointed  sheath  was  always  first  to  appear  when  the  thrust  was  made ; 
second,  that  the  darts  inside  the  sheath  worked  back  and  forth  alter- 
nately, and  quite  independently  of  the  sheath  or  of  one  another ;  third, 
that  the  poison  was  exuded  in  droplets  from  the  tip  of  the  sting  between 
the  darts.  Beyond  these  points,  observation  of  the  mechanism  of  the 
sting  was  impossible,  but  the  description  of  Cheshire's  observations 
gives  a  very  clear  and  plausible  explanation. 

"  The  sheath  has  three  uses ;  first,  to  open  the  wound ;  second,  to 
act  as  an  intermediate  conduit  for  the  poison;  and  third,  to  hold  in 
accurate  position  the  long-barbed  darts.  The  sheath  does  not  inclose 
the  darts  as  a  scabbard,  but  is  cleft  down  the  side  which  is  below,  when 
the  sting  points  backward.  The  darts,  as  soon  as  their  ugly  barbs 
establish  a  hold,  first  one  and  then  another  drive  back  and  forth  by  suc- 
cessive blows.  These  in  turn  are  followed  by  the  sheath,  when  the 
darts  again  plunge  more  deeply,  until  the  murderous  little  tool  is  buried 
to  the  hilt.     But  these  movements  are  the  result  of  a  muscular  appara- 


VENOMOUS   INSECTS  AND   ARACHNIDS  357 

tus  yet  to  be  examined.  The  dovetail  guide-rails  of  the  sheath  are 
continued  far  above  its  bulbous  ])ortion,  and  along  with  these  the  darts 
are  also  prolonged  upward,  still  held  to  the  guides  by  the  grooved 
arrangement ;  but  both  guides  and  darts,  in  the  upper  part  of  their 
length,  curve  from  each  other  like  the  arms  of  the  Y,  before  mentioned, 
to  points  C,  C  (Fig.  215)  where  the  darts  make  attachment  to  two 
levers  (i,  i').  The  levers,  or  plates,  as  they  are  called  (A7  and  K'l"),  are 
provided  with  broad  muscles,  which  terminate  by  attachment  to  the 
lower  segments  of  the  abdomen.  These,  by  contraction,  revolve  the 
levers  aforesaid  round  the  points  /,  /',  so  that  without  relative  move- 
ment of  rod  and  groove,  the  points  c,  c'  approach  each  other.  The 
arms  of  the  Y  straighten  and  shorten,  so  that  the  sheath  and  darts  are 
driven  from  their  hiding  place  together  and  the  thrust  is  made  by  which 
the  sheath  produces  its  incision  and  fixture.  The  sides  being  sym- 
metrical, we  may,  for  simplicity's  sake,  concentrate  our  attention  on 
one,  say  the  left  in  the  figure.  A  muscular  contraction  of  a  broad  strap 
joining  K  and  D  (the  dart  protractor)  now  revolves  k  on  I,  so  that  a 
is  raised,  by  which  clearly  c  is  made  to  approach  d;  that  is,  the  dart  is 
sent  forward,  so  that  the  barbs  extend  beyond  the  sheath  and  deepen 
the  puncture.  The  other  dart,  and  then  the  sheath,  follow,  in  a  se- 
quence already  explained,  and  which  G  is  intended  to  make  intelligible, 
representing  the  entrance  of  the  sheath,  h  the  advance  of  the  barbs, 
and  c  the  sheath  in  its  second  position.  The  barb  retractor  muscle  is 
attached  to  the  outer  side  of  i,  and  by  it  a  is  depressed  and  the  barbs 
lifted.  These  movements,  following  one  another  with  remarkable 
rapidity,  are  entirely  reflex,  and  may  be  continued  long  after  the  sting 
has  been  torn,  as  is  usual,  from  the  insect.  By  taking  a  bee  under  the 
microscope  and  forcing  the  sting  into  action,  the  sting  movement  will 
be  seen  to  be  kept  up  by  continued  impulses  from  the  fifth  abdominal 
ganglion  and  its  multitudinous  nerves,  which  penetrate  every  part  of  the 
sting  mechanism  and  may  be  traced  even  into  the  darts.  These  facts 
will  show  why  an  abdomen  separated  many  hours  may  be  able  to  sting 
severely,  as  I  have  more  than  once  experienced." 

Sting  in  Situ.  —  It  can  readily  be  seen  that  the  sting  originates  from 
the  seventh  and  eighth  segments  and  lies  between  the  oviduct  and  the 
rectum  above.  The  darts  of  the  sting  follow  the  ventral  line  of  the  ab- 
domen and  are  held  in  place  by  the  sheath  situated  just  above,  while 
the  barbs  of  the  darts  are  pointing  downward  and  outward.  In  a  space 
above  the  sheath  lie  the  fleshy  palpi.  The  delicate  attachment  between 
the  sting  and  the  organs  of  the  abdomen  is  here  indicated,  for  only  a 
small  portion  of  the  sting,  in  comparison  with  its  size,  has  any  connection 
with  parts  in  the  abdomen.  This  accounts  for  the  ease  with  which  the 
sting  is  torn  from  the  abdomen  when  the  barbs  become  imbedded  after 
a  thrust  of  the  darts  is  made. 

Stinging  Insects.  —  The  stinging  insects  belong  to  the  order  Hy- 
menoptera,  suborder  Aculeata,  and  are  best  known  as  the  ants,  bees, 


358       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


and  wasps,  in  which  the  females  of  all  species  are  provided  with  a  spe- 
cialized ovipositor  known  as  a  sting,  more  or  less  well  developed  for 
piercing  the  skin  of  higher  animals  or  other  insects.  The  sting  is  used 
either  as  an  organ  of  defense  or  offense,  in  the  latter  case  often  to  procure 
food  for  the  young. 

The  principal  aculeate  Hymenoptera  are  divided  into  the  following 
superfamilies :  viz. :  Formicina,  the  true  ants ;  Sphecina,  the  digger 
wasps ;   Vespina,  the  true  wasps ;  and  Apina,  the  bees. 

The  superfamily  Formicina  includes  the  true  ants,  which  are  divided 
into  three  or  more  families,  Formicidse,  Poneridse,  and  Myrmicidse. 
One  of  the  most  formidable  stinging  ants  in  California  is  Pogonomyrmex 
californicus  Buck.  This  ant  will  not  only  attack  humans  but  also  smaller 
domesticated  animals.  Thus  hog  raisers  in  the  Imperial  Valley,  Cali- 
fornia, report  many  pigs  killed  by  ants,  one  farmer  reporting  a  loss  of  400 
small  pigs  during  one  year  and  another  100  to  150  during  a  period  of  three 
years,  —  all  killed  by  ants. 

Ants  of  this  species  are  very  abundant  in  the  Imperial  Valley,  and  it 
is  a  matter  of  common  observation  to  see  a  small  pig  walk  leisurely  upon 

an  ant  mound  and  suddenly  begin  to  kick 
and  squeal,  due  to  the  terrific  attack  of 
the  myriads  of  ants  rushing  forth  from 
the  nest.  The  writer  has  meager  experi- 
mental evidence  to  deny  the  popular  opin- 
ion above  stated.  The  pig  is  certainly 
very  uncomfortable  during  the  attack,  but 
experimental  evidence  of  paralysis  and 
death  due  to  the  ants  has  not  been  se- 
cured. However,  much  more  work  needs 
to  be  done  to  safely  deny  the  statements 
of  practical  hog  raisers. 

The  ants  may  be  destroyed  by  apply- 
ing kerosene  to  the  nests,  using  a  funnel 
or  hollow  rod  to  reach  the  deeper  parts ; 
potassium  cyanide  in  liquid  form  may  also 
be  used,  but  great  care  must  be  exercised 
both  in  the  preparation  and  application 
of  the  same  owing  to  its  very  poisonous 
nature. 

Among  the  Vespina,  the  best-known  stinging  species  belong  to  the 
family  Mutillidse,  the  velvet  ants,  also  known  as  the  woolly  ants,  cow 
killers,  etc.  (Fig.  216).  The  velvet  ants  are  covered  with  hair  and 
the  body  is  commonly  banded  with  two  or  more  strongly  contrasting 
colors.  There  are  very  many  species  of  Mutillids,  most  of  which 
measure  from  i  to  1  inch  in  length.  A  very  common  species  in  the 
central  states  of  the  United  States  is  S phcBrophthalmia  occidentalis 
Linn.,  a  black  species  with  a  scarlet  band.     This  species  is  very  com- 


FiG.  216. — A  velvet  ant  (Mutilla), 
also  known  as  a  "cow  killer." 
X2.2. 


VENOMOUS   INSECTS  AND   ARACHNIDS 


359 


mon  on  the  beach  sands  of  Lake  Erie,  causing  bare-foot  bathers  much 
distress. 

Many  of  our  large  dusty  yellow  to  cinnamon  colored  species  belong 
to  the  genus  Mutilla  and  are  commonly  called  "  cow  killers  "  (Fig.  216). 
These  occur  abundantly  among  dry  leaves  along  the  roadside  or  by- 
paths in  the  woods. 

To  the  Vespina  also  belong  the  yellow  jackets  or  hornets,  Vespa 
maculata  Linn.,  and  other  species  which  build  large  nests  in  the  branches 
of  trees,  also  the  mud  daubers  Pelopoeus  cementarius  Drury,  Polides 
imlUpes  Lep.,  and  Polyhia  fiavitarsis  Sauss.,  et  al.     These  species  with 

their    relatives    belong     

to  the  family  Vespidse, 
and  all  have  a  well- 
developed  sting  which 
may  be  used  on  the 
least  provocation. 

Of  the  solitary 
w^asps  belonging  to  the 
superfamily  Sphecina, 
the  great  digger  wasp 
or  "  cicada  killer," 
Sphecius  speciosus  Say 
(Fig.  217),  is  the  most 
formidable.  This  spe- 
cies, a  member  of  the 
family  Bembecidae,  is 
nearly  an  inch  and  a 
half  in  length,  is  black  with  yellow  segmentally  arranged  partial  bands 
on  the  abdomen.  This  wasp  easily  brings  to  earth  very  large  cicadas, 
carries  its  prey  to  a  previously  prepared  burrow  where  eggs  are  de- 
posited and  the  larvse  develop  in  the  cicada. 

Underground  wasps'  or  hornets'  nests  may  be  treated  successfully 
with  carbon  bisulphide,  while  sulphur  fumigation  or  thorough  spraying 
with  kerosene  will  suffice  to  destroy  the  nests  of  wasps  built  in  the 
branches  of  the  trees.     Night  treatment  is  suggested. 

The  true  bees  belong  to  the  superfamily  Apina,  the  honeybee  Ajns 
mellifera  Linn.,  a  member  of  the  family  Apidse,  and  the  bumblebee 
Bombus  fervidus  Fabr.  and  others  belonging  to  the  family  Bombidse. 


Fig.  217.  —  A  digger  wasp  {Sphecius  speciosus).      X  1-1. 


Spiders 

Class   Arachnida  —  Order  Araneida 

Characteristics  of  the  Araneida.  —  All  spiders  belong  to  the  order 
Araneida  in  which  the  abdomen  is  sac-like  and  unsegmented,  joined  to 
the   cephalothorax   b}^   a   slender   pedicel.     According   to   Comstock  ^ 

1  Comstock,  John  Henry,  1912.  The  Spider  Book.  Doubleday,  Page  & 
Co.     XV  +  731  pp. 


360       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

the  chelicerse  are  usually  claw-like,  "  folded  back  into  a  groove  in  the 
basal  segment,  like  the  blade  of  a  pocketknife  into  a  handle,"  i.e.  uncate  ; 
or  they  may  be  pincer-like  (chelate),  "  there  being  a  prolongation  of  the 
first  segment  which  is  opposed  to  the  claw."  The  pedipalps  are  more  or 
less  leg-like.  The  four  pairs  of  legs  are  all  fitted  for  walking.  There  are 
usually  present  eight  eyes  but  these  may  be  reduced  to  six,  four,  two  or 
none.  The  respiratory  organs  of  spiders  are  either  book  lungs  or  trachecB, 
or  in  most  species  a  combination  of  the  two.  The  book  lungs  are  sacs 
which  open  on  the  ventral  side  of  the  abdomen  by  means  of  slit-like  spir- 
acles. Within  each  sac  there  is  a  series  of  lamellate  folds.  The  tracheae 
are  far  less  developed  than  in  insects  and  are  much  more  localized. 

The  Araneida  are  divided  into  more  than  thirty  families. 

Spider  Venoms.  —  All  spiders  secrete  venom  by  means  of  which  they 
kill  their  prey.  The  venom  glands  are  located  in  the  anterior  portions  of 
the  cephalothorax  and  are  two  in  number.  "  Each  gland  discharges 
its  product  through  a  long  slender  duct  which  opens  near  the  tip  of  the 
claw  of  the  chelicera  of  the  corresponding  side  of  the  body.  This  open- 
ing is  so  placed  that  it  is  not  closed  by  the  pressure  of  the  bite,  but  allows 
the  venom  to  flow  into  the  wound.  In  the  tarantulas  each  gland  is  situ- 
ated in  the  basal  segment  of  a  chelicera.  The  glands  are  sac-like  in  form  ; 
the  lumen  of  the  sac  serves  as  a  reservoir  of  venom  ;  the  wall  is  composed 
of  excreting  cells,  supported  by  a  layer  of  connective  tissue,  and  there  is 
a  layer  of  muscle  fibers  surrounding  the  sac  "  (Comstock). 

While  spider  venom  is  very  destructive  to  the  life  of  insects  upon 
which  spiders  prey,  there  is  little  evidence  (with  certain  exceptions) 
to  indicate  that  this  venom  is  injurious  to  man.  Most  of  our  so-called 
spider  bites  are  traceable  to  other  sources,  particularly  cone-noses 
(Reduviidse).  Comstock  (1912,  Joe.  cii.)  has  given  much  attention  to 
this  matter  and  has  come  to  the  conclusion  that  there  are  no  spiders 
that  need  be  feared  in  the  northern  part  of  the  United  States  at  least, 
and  in  the  South  there  is  only  one  dangerous  genus,  Latrodedes.  As 
to  the  so-called  tarantula  (Heteropoda)  which  is  brought  to  the  North 
in  bunches  of  bananas  Comstock  has  the  following  to  say  :  "  This,  how- 
ever, although  a  large  spider  is  an  inoffensive  one.  Mr.  John  T.  Lloyd 
informs  me  that  he  has  collected  scores  of  specimens  of  this  species  with 
his  hands  in  Samoa,  where  it  is  abundant,  and  has  never  been  bitten  by 
it." 

The  Hourglass  Spider  {Latrodedes  madans  Fabr.),  also  known  as 
the  "  black  widow  "  or  "  shoe  button"  spider,  is  a  medium-sized,  glossy 
black,  naked  spider.  The  females  measure  from  one  to  one  and  a 
fourth  inches  in  length  over  all,  while  the  males  are  less  than  an  inch  in 
length.  The  abdomen  is  globose,  marked  ventrally  with  brick-red 
triangular  spots  (Fig.  218).  These  spots  vary  in  arrangement,  —  often 
two  of  these  touch  base  to  apex,  or  apex  to  apex,  not  unlike  an 
hourglass  in  outline,  or  there  may  be  four,  roughly  arranged  like  a  Mal- 
tese cross ;   in  some  individuals  only  one  spot  may  be  seen.     The  males 


VENOMOUS   INSECTS  AND   ARACHNIDS 


361 


and  immature  females  are  variously  striped  and  spotted  with  lighter 
markings.     The  species  belongs  to  the  family  Theridiidse. 

Latrodectes  mactans  occurs  quit  ecommonly  in  California  and  the 
South,  also  the  West  Indies,  Madagascar,  New  Zealand  and  Algeria, 


Fig.  218.  — -A  venomous  spider,  Latrodectes  mactans 


and  has  the  reputation  of  being  extremely  venomous.  Sundry  speci- 
mens have  been  sent  to  the  writer  at  various  times,  and  occasional  re- 
ports of  its  having  caused  dangerous  and  even  fatal  illness  in  California 
have  been  made,  but  unfortunately  very  little  experimental  evidence 
seems  to  be  available. 

An  account  of  a  fatal  case  in  North  Carolina  is  given  by  Packard  and 
Howard,^  viz. :  An  employee  (farm  laborer  engaged  in  hauling  wood) 
of  Mr.  John  M.  Dick  is  reported  to  have  been  bitten  by  a  black  spider 

1  Packard,  A.  S.,  and  Howard,  L.  O.,  1899.  A  contribution  to  the  literature 
of  fatal  spider  bites.     Insect  Life,  Vol.  1,  No.  7,  pp.  204-211. 


382       MEDICAL  AND   VETERINARY   ENTOMOLOGY 

with  a  red  spot  on  it  at  about  8.30  o'clock  a.m.,  dying  of  the  effects 
about  fourteen  hours  later,  i.e.  betAveen  10  and  11  o'clock  p.m.  The 
victim  is  said  to  have  felt  something  crawling  on  his  neck,  and  as  he 
brushed  it  off  it  bit  him  very  severely,  causing  very  great  pain.  The 
cause  was  described  as  being  a  black  spider  with  red  spots.  An  examina- 
tion of  the  neck  revealed  ten  little  white  pimples,  all  of  which  could  be 
covered  with  a  one-dollar  silver  coin ;  no  puncture  was  seen.  There 
was  no  swelling,  but  the  neck,  left  breast  and  arm  were  so  hard  that  no 
impression  could  be  made  with  the  thumb.  The  man  complained  of 
pain  running  through  his  entire  body.  It  should  be  noted  that  the  man 
was  perfectly  healthy.  By  one  o'clock  the  pain  had  settled  in  his  bowels 
and  shortly  thereafter  he  was  attacked  with  spasms.  About  four  o'clock 
spasms  recurred  and  the  patient  lapsed  into  unconsciousness  and  re- 
mained so  until  death. 

In  the  same  paper  the  authors  refer  to  the  investigation  of  Dr.  Graells, 
appointed  by  the  Academy  of  INIedicine  and  Surgery  at  Barcelona  in 
1833  to  investigate  the  reported  venomous  nature  of  the  "  Malmignatte  " 
of  southern  Europe  (Latrodectes  malmigniatus  Walck).  Graells  re- 
ported the  following  symptoms : 

"  A  double  puncture  surrounded  by  two  red  circles,  which  unite,  together 
forming  an  edematous  areole  which  marks  the  seat  of  a  tumor  which  develops 
later.  The  pain  extends  and  soon  occupies  the  length  of  the  bitten  limb,  and 
often  reaches  the  axillary  or  inguinal  glands,  according  to  the  limb  bitten. 
These  glands  tumefy  and  become  painful  and  the  skin  between  them  and  the 
bite  becomes  marked  with  livid  spots  which  seem  to  follow  the  course  of  the 
lymphatic  vessels.  The  pain  continues,  reaching  the  body  even  to  the  ab- 
dominal and  thoracic  cavities,  with  a  sensation  of  burning  heat,  strong  con- 
striction or  soreness  of  throat,  tension  of  the  abdomen,  tenesmus,  and  extreme 
headache,  which  makes  itself  felt  along  the  spinal  column ;  soon  followed  by 
general  convulsions,  more  particularly  in  the  extremities,  followed  by  insensi- 
bility, especialh^  in  the  feet,  which  are  ordinarily  livid,  while  the  whole  body  is 
swollen.  This  imposing  array  of  symptoms  brings  about  a  very  marked  low 
spirit  on  the  part  of  the  patients,  indicated  by  their  expressions  of  despair,  of 
profound  affliction,  or  fear  concerning  the  return  of  the  health,  for  they  be- 
lieve themselves  threatened  with  approaching  death. 

"They  continually  change  from  place  to  place  in  their  bed,  giving  utterance 
to  sighs  and  plaintive  cries,  carrying  their  hands  to  their  heads  mechanically, 
or  thej^  say  that  they  feel  their  brain  pricked  l^y  pins.  The  face  is  sometimes 
red  and  burning  or  others  pale.  The  difficulty  of  respiration  is  marked,  the 
pulse  is  very  low,  quick,  irregular,  the  skin  cold  and  rather  moist  from  an  abun- 
dant cold  and  viscid  perspiration ;  at  the  same  time  the  patient  complains 
that  his  bowels  are  burning  and  asks  for  fresh  water.  In  some  cases  the  sight 
is  almost  totally  obscured,  and  conjunctiva  injected  ;  in  others  the  voice  becomes 
weakened,  and  perhaps  a  ringing  in  the  ears  fjecomes  very  marked.  Sometimes 
livid  spots  appear  over  the  whole  body.  The  intensity  of  these  s^Tiiptoms  varies 
according  to  the  susceptil)ility  of  the  individual,  to  the  strength  of  the  Latro- 
dectes, and  also  the  number  of  bites  which  the  patient  has  received. 

"Recovery  comes  sooner  or  later  according  to  the  strength  of  the  patient, 
the  energy  of  the  remedies,  and  the  promptness  of  their  effect.  In  all  cases  it  is 
announced  by  the  perspiration,  which  from  cold  and  viscid  becomes  warm  and 
vaporous ;  by  the  quickening  and  regularity  of  the  pulse ;  by  increasing  facility 


VENOMOUS   INSECTS  AND  ARACHNIDS 


363 


in  respiration  and  urination  ;  bj'  the  cessation  of  the  inflammation  of  the  glands 
and  of  the  aching  in  the  brain  and  spinal  cord,  which  passes  into  a  sort  of  lethargy 
which  may  be  more  the  effect  of  the  laudanum  given  than  a  symptom  of  the 
disease." 

In  many  respects  the  above  symptoms  apply  to  the  two  cases  reported 
to  the  writer  by  the  late  Mr.  Charles  Fuchs,  Curator  of  Insects,  Cali- 
fornia Academy  of  Science ;  however,  the  local  effects  in  these  two  cases 
were  very  much  more  severe. 

According  to  Comstock  (1912,  loc.  cit),  Merriam  (1910)  in  "  The 
Daion  of  the  World,  Myths  and  Weird  Tales  told  by  the  Mewan  Indians  of 
California,"  the  Northern  Mewuk  says  :  "  Po'ho-noo  the  small  black  spider 
with  a  red  spot  under  his  belly  is  poison.  Sometimes  he  scratches  people 
with  his  long  fingers,  and  the  scratch  makes  a  bad  sore.  ...  All  the 
tribes  know  that  the  spider  is  poisonous  and  some  of  them  make  use  of 
the  poison."  The  latter  states  also  that  the  California  Indians  rank 
this  spider  with  the  rattlesnake  as  poison,  and  mash  the  spider  to  rub 
the  points  of  their  arrows  in  it. 

Habits  and  Life  History  of  Latrodectes  mactans.  —  This  spider 
occurs,  when  in  its  geographical  range,  not  uncommonly  in  old  out- 
buildings, old  barns,  stables,  w^oodpiles,  etc.  It  spins  a  rough  web  in 
Avhich  it  catches  its  prey,  mainly  flies 
and  other  insects.  It  is  an  exceed- 
ingly aggressive  species,  as  the  writer 
has  observed  in  the  several  grown 
individuals  under  observation  at 
various  times  in  the  laboratory.  The 
egg  cocoons  (Fig.  219)  are  spun  dur- 
ing the  summer,  and  are  well  pro- 
tected by  the  web  and  carefully 
guarded  by  the  female.  Each  egg 
cocoon  contains  three  hundred,  more 
or  less,  rather  large  eggs.  The  in- 
cubation period  in  observed  cases  at 
a  maintained  temperature  of  27  ± 
1°  C.  was  about  thirty  days,  —  for 
example  a  spider  spun  her  egg  cocoon 
during  the  night  of  July  17,  the  eggs  hatching  during  the  night  of 
Aug.  13.  Seven  egg  cocoons  w-ere  spun  by  one  spider,  but  the  eggs 
contained  in  the  seventh  did  not  hatch. 

The  young  spiders  (Fig.  220)  are  gray,  quite  unlike  the  adult  in  this 
respect,  and  are  very  active,  attacking  plant  lice,  etc.  at  once.  The  first 
molt  takes  place  within  a  week,  followed  by  numerous  molts  at  intervals 
of  a  week  or  more.  The  young  spiders  grow  darker  with  each  molt, 
with  the  appearance,  however,  of  creamy  w^hite  lines  or  spots  dorsally  on 
the  abdomen.  The  reddish  ventral  markings  appear  within  a  month 
ordinarily.     Growth  is  very  rapid  during  the  rest  of  the  summer  and 


Fig.    219.  —  Egg    cocoon    of   Latrodectes 
mactans.       X  2. 


364       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

autumn,  but  maturity  is  not  reached  until  the  following  spring  or  early 
summer. 

Tarantulas.  —  The  term  tarantula  is  applied  to  the  very  large  spiders 
belonging  to  the  F'amily  Aviculariida?  occurring  in  California  and  other 
tropical  and  subtropical  climates.  The  best-known  species  in  California 
is  Eurypehna  (Mygale)  hentzii  Girard,  also  known  as  a  bird  spider,  as 

is  Avicularia  californica  Banks. 
While  these  spiders  are  much 
dreaded  there  is  little  or  no  evi- 
dence to  warrant  this  fear.  The 
common  trapdoor  spider  of  Cali- 
fornia is  Bothriocyrtum  californi- 
cuin  Cambridge,  also  greatly 
feared  by  many  persons. 

The   term    tarantula  was  first 
applied  to  an  European  species. 

Fig.  220.  —  Young  stages  of  Latrodectesmac-     lycosa  tarentula,  which  according 
tans.     Lett,  ventral  view,  showing  reddish         "^  ^  '  " 

hourglass-like  marking  on  abdomen ;  right,     to    Comstock    doCS    not    belong    to 

darrlnlildAgJ^'^x  3.''^"*'  abdomen  with    ^^e  spiders  to  which  this  term  is 

applied  in  America. 

To  the  bite  of  Lycosa  tarentula  is  referred  the  hysterical  disease  known 
as  tarantism  said  to  have  been  common  in  southern  Europe  in  the 
Middle  Ages. 

The  following  account  of  tarantism  is  taken  from  the  Cambridge 
Natural  History,  Vol.  IV,  p.  361 :  "  The  bite  of  the  spider  was  supposed 
to  induce  a  species  of  madness  which  found  its  expression  —  and  its  cure 
—  in  frantic  and  extravagant  contortions  of  the  body.  If  the  dance 
was  not  sufficiently  frenzied,  death  ensued.  In  the  case  of  survivors, 
the  symptoms  were  said  to  recur  on  the  anniversary  of  the  bite.  Particu- 
lar descriptions  of  music  were  supposed  to  incite  the  patient  to  the  ex- 
cessive exertion  necessary  for  his  relief ;   hence  the  name  '  Tarantella.' 

"  In  the  middle  ages  epidemics  of  '  tarantism  '  were  of  frequent  oc- 
currence and  spread  with  alarming  rapidity.  They  were  seizures  of  an 
hysterical  character,  analogous  to  the  ancient  Bacchic  dances,  and  quite 
unconnected  with  the  venom  of  the  spider  from  which  they  took  their 
name.  The  condition  of  exaltation  and  frenzy  was  contagious,  and 
would  run  through  whole  districts,  with  its  subsequent  relapse  to  a  state 
of  utter  prostration  and  exhaustion.  The  evil  reputation  of  the  Taran- 
tula appears  to  have  exceedingly  little  basis  in  fact." 

Venomous  Ticks 

Class  Arachnida,  Order  Acarina 

Ticks  producing  local  or  systemic  disturbances  by  their  bite  alone 
are  known  in  both  families,  Ixodidae  and  Argasidee  (see  Chap.  XVIII), 
though  more  commonly  in  the  latter. 


VENOMOUS   INSECTS  AND   ARACHNIDS  365 

Ordinarily  little  or  no  injury  results  from  the  mere  bite  of  an  Ixodine 
tick,  —  the  writer  has  known  of  Dermacentor  occidentalis  Neumann  and 
Dermacentor  variabilis  Say  to  remain]attached  to  a  person  for  days  without 
causing  great  inconvenience  and  occasionally  quite  unobserved  by  the 
host.  However,  Nuttall  (1911,  loc.  cit.,  p.  133)  records  a  number  of  cases 
cited  by  other  authors  in  which  the  bite  of  Ixodes  ricinus  Linn,  has  caused 
serious  consequences,  notably  a  case  described  by  Johannessen  of  a  "  boy 
where  the  tick's  body  was  removed  but  the  capitulum  remained  em- 
bedded in  the  skin  at  the  back  of  the  head.  Swelling  followed  at  the 
point  of  injury,  accompanied  by  headache,  stiffening  and  cramps  in  the 
muscles  of  one  side,  partial  loss  of  memory  and  polyuria ;  the  pupils 
became  dilated,  etc.  The  boy  made  a  slow  recovery."  Blanchard  is 
quoted  by  the  same  author  as  stating  "  that  accidents  of  a  grave  char- 
acter occasionally  follow  ricinus  bites,  the  wound  serving  as  a  center  from 
which  infection  may  spread  to  the  rest  of  the  body." 

Quite  a  number  of  species  included  in  the  Family  Argasidse  are 
known  to  cause  more  or  less  serious  consequences  by  their  bites,  notably 
Ornithodorus  moubata  Murray,  0.  coriaceus  Koch,  and  Argas  persicus 
Neumann. 

Ornithodorus  luoubata  Murray  (see  Chapter  XVIII)  has  been  re- 
ported repeatedly  as  causing  marked  consequences  by  its  bite.  Well- 
man  as  quoted  by  Nuttall  (1908,  he.  cit.,  p.  98)  "  states  that  the  bite 
is  very  painful,  the  swelling  and  irritation  (especially  in  Europeans) 
not  subsiding  for  days.  The  wheals  are  hard,  raised  and  swell  most 
disagreeably  if  scratched,  and  this  even  a  week  after  being  bitten.  The 
bite  of  young  ticks  (nymphse)  is  said  by  the  natives  to  be  more  severe 
than  that  of  the  adults." 

Ornithodorus  coriaceus  Koch.  —  The  attention  of  the  writer  has 
been  repeatedly  called  to  a  very  venomous  species  of  tick  commonly 
known  as  the  "  Pajaroello  bug  "  occurring  in  isolated  sections  of  Califor- 
nia and  Mexico.  Reports  invariably  indicate  that  the  bite  of  a  single 
individual  produces  very  severe  and  often  grave  results.  In  conversa- 
tion with  natives  it  was  learned  that  this  creature  was  more  feared  than 
the  rattlesnake.  Many  harrowing  tales  are  told  regarding  the  loss  of 
an  arm  or  leg  or  even  death  due  to  the  bite  of  this  tick.  No  doubt 
much  of  this  is  greatly  exaggerated ;  however,  the  infected  bite  might 
easily  lead  to  grave  consequences.  Mr.  W.  L.  Chandler,  a  graduate 
student  in  the  University  of  California,  has  given  the  writer  an  accurate 
account  of  two  bites  which  he  suffered  while  stationed  in  the  San  Antone 
Valley  (California).  The  first  bite  was  received  July  2,  1912.  He 
experienced  a  sharp  pain  on  the  left  arm  and  upon  rolling  up  his  sleeve 
discovered  a  large  tick,  partly  engorged,  attached  to  the  upper  arm  in 
front.  He  dislodged  the  tick  and  sucked  the  lesion.  The  lesion  when 
first  discovered  showed  a  small  dark  purple  ring  surrounding  a  bright 
red  spot,  the  point  of  attachment.  The  discoloration  disappeared  in  a 
short  time,  but  the  arm  was  "  highly  irritable  for  two  or  three  days  and 


366       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

at  the  point  of  attachment  a  minute  clear  scab  formed."  The  tick 
proved  to  be  a  "  pajaroello." 

The  second  bite  took  place  July  16  while  seated  in  a  thicket  of 
willows  (the  first  bite  took  place  while  riding  over  a  brush-grown  hill), 
and  in  this  case  the  sharp  pain  involved  the  left  leg.  An  almost  fully 
engorged  tick  (again  a  pajaroello  measuring  about  f  of  an  inch  in  length 
and  about  ^  inch  in  width  was  removed  from  just  above  the  shin.  Once 
more  a  bright  red  spot  was  visible  at  the  point  of  attachment,  surrounded 
by  an  irregular  purple  ring  about  three-fourths  of  an  inch  in  diameter. 
In  about  an  hour  the  leg  began  to  swell  in  the  vicinity  of  the  lesion,  and 
in  about  three  hours  the  entire  lower  leg  was  tremendously  swollen. 
The  coloration  about  the  point  of  attachment  had  widened  considerably, 
was  puffy  and  a  clear  lymph  exuded  freely  from  the  lesion.  The  young 
man  lanced  the  leg,  causing  the  blood  to  flow  freely,  and  treated  the  wound 
with  crystals  of  potassium  permanganate,  binding  the  leg  with  cotton 
and  gauze.  During  the  following  night  he  reports  experiencing  a 
general  disagreeable  feeling,  the  entire  lower  leg  "irritable  and  numb." 
On  the  following  day  the  bite  on  the  arm  became  irritable  again,  and  was 
treated  as  had  been  the  leg,  fearing  bad  results.  For  several  weeks 
both  lesions  exuded  a  clear  lymph  from  beneath  an  "oily-looking,  trans- 
parent, red  mottled  scab  "  which  remained  in  evidence  for  two  or  three 
months. 

Chandler  reported  these  ticks  very  numerous  in  some  localities,  having 
counted  as  high  as  six  within  half  an  hour  crawling  over  a  saddle  blanket 
placed  on  the  ground.  Their  presence  and  number  seemed  to  be  de- 
termined by  the  presence  of  cattle,  although  ticks  were  found  where 
there  were  no  cattle  but  in  places  which  were  evidently  favorite  haunts 
of  large  wild  animals. 

Experiments  with  the  Pajaroello.  —  A  number  of  specimens  of 
Ornithodorus  coriaceus  were  collected  in  the  San  Antone  Valley  and  at 
Newman,  California,  for  purposes  of  experimentation  and  study  of  life 
history.  In  cooperation  with  Dr.  W.  A.  Sawyer  and  Messrs.  S.  W. 
Newman  and  W.  L.  Chandler,  the  writer  conducted  a  number  of  experi- 
ments particularly  with  reference  to  the  bite.  In  one  of  these  experi- 
ments a  mature  female  tick  {Ornithodorus  coriaceus)  was  permitted  to 
bite  a  nearly  full-grown  monkey  (Macacus  rhesus)  twice  with  an  interval 
of  sixteen  days  intervening  })etw^een  the  two  bites.  The  tick  was  ap- 
plied at  9:42  a.m.  Dec.  10,  1913  and  began  sucking  blood  at  9:43, 
one  minute  later,  becoming  engorged  and  falling  off  at  10:21  a.m.,  a 
period  of  38  minutes.  At  10  :  30  a  few  minutes  after  the  tick  dropped  off 
there  appeared  a  deep  red  hemorrhagic  area  2  mm.  in  diameter  at  the 
point  of  biting  with  a  somewhat  lighter  area  10  mm.  in  diameter  sur- 
rounding the  central  area.  At  10  :  27  there  was  a  black  spot  at  the  point 
of  bite  1.5  mm.  in  diameter,  the  inner  red  hemorrhagic  area  measuring 
4  mm.,  with  a  yellowish  wdiite  area  surrounding  this  8X6  mm.,  and  an 
outer  red  petechial  area  15  X  13  mm.     No  general  symptoms  were 


VENOMOUS   INSECTS  AND  .  ARACHNIDS 


367 


noted.  As  shown  in  Fig.  221  the  lesion  reached  its  greatest  expanse 
the  following  day  when  the  following  measurements  were  taken :  — 
dark  purple  spot  2  mm.  in  diameter  (a  very  dark  red  scab) ;  the  inner 
red  area  6X5  mm.,  the  yellowish  white  area  20  X  12  mm.,  the  outer 
area  48  X  23  mm.  and  fading.  The  yellowish  white  area  including 
bite  was  slightly  swollen.  By  Dec.  14,  i.e.  four  days  after  the  bite  was 
received,  the  ecchymosis  had  entirely  disappeared  ;  by  Dec.  16,  six  days 


Fig  2'n  —  Showing  venomous  tick  iOniithodnni.s  ronnaus}  an.l  lesion  produced  by  same 
on  skin  of  a  monkey.  (1)  tick  on  skin  before  attaching ;  (2)  tick  attached  and  fully 
engorged-  lesion  appears  as  dark  shadow  at  anterior  end  of  tick;  (3)  shows  lesion 
within  a  few  minutes  after  tick  has  dropped  off ;  (4)  lesion  at  expiration  of  five  hours ; 
(5)  lesion  at  expiration  of  twenty-four  hours.  (For  description  and  extent  of  areas  see 
text.)       X  .7. 

after  the  bite,  the  lesion  was  entirely  gone  but  for  a  slight  pigmentation, 
a  thickened  reddish  area  measuring  5X3  mm.  and  a  small  scab  2  mm. 
in  diameter. 

The  monkey  remained  normal  throughout  the  experiment  as  regards 
temperature,  weight,  blood  count  and  general  condition. 

The  second  bite  was  received  by  the  same  animal  on  Dec.  26,  the 
tick  being  applied  at  9  :  43  a.m.,  taking  hold  at  9  :  44  a.m.,  and  dropping 
off  fully  engorged  at  9 :  55  a.m.,  requiring  but  11  minutes  to  engorge. 
The  history  of  the  second  bite  follows  that  of  the  first  very  closely,  ex- 


368       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

cept  for  the  extent  of  the  lesion,  which  was  greater,  i.e.  70  X  31  mm.  In 
order  to  note  any  manifestations  on  the  part  of  the  first  lesion,  the  second 
bite  was  located  near  the  opposite  nipple.     No  change  was  observed. 


Fig.  222.  —  Showing  Ornithodorus  coriaceus  just  backing  away  from  her  eggs  recently  de- 
posited in  the  sand.     Note  the  protective  coloration  of  the  tick.       X  5. 

The  lesion  produced  by  the  second  bite  had  disappeared  by  December 
31,  i.e.  five  days  after  the  bite,  except  for  a  slight  thickening  3  mm.  in 
diameter  and  a  slight  white  scale  at  the  center.     Again  the  monkey  had 


VENOMOUS  INSECTS  AND   ARACHNIDS  369 

remained  normal,  except  for  a  slight  increase  in  the  count  of  white  blood 
corpuscles,  which  rose  from  7400  at  the  time  of  the  bite  to  13,900  by 
noon  of  the  same  day,  going  down  again  to  7300  by  5  p.m. 

Life  History  of  Ornithodorus  coriaceus.  —  The  pajaroello  deposits 
large  plum-colored  spherical  eggs  (Fig.  222).  In  the  laboratory  these 
are  deposited  on  the  sand  in  slight  depressions.  There  are  commonly 
four  to  seven  layings  at  intervals  of  from  several  days  to  several  weeks 
during  the  months  of  JNIay  to  July,  inclusive  (as  early  as  February  under 
laboratory  conditions),  and  the  female  is  known  to  deposit  eggs  for  at 
least  two  successive  seasons.  The  number  of  eggs  observed  per  laying 
has  been  61  to  323,  with  a  total  of  from  747  to  1158  for  one  season.  The 
incubation  period  at  a  maintained  temperature  of  from  24°  to  26°  C.  is 
from  19  to  29  days,  with  an  average  of  about  22  days. 

The  larvae  (Fig.  223)  are  very  active,  scattering  quickly  and  attach- 
ing readily  to  a  host,  particularly  rabbits.  Experimentally  the  human 
has  also  served  as  a 
larval  host.  The  ear 
of  a  rabbit  apparently 
affords  a  most  satis- 
factory point  for  at- 
tachment. The  larva 
remains  attached  to 
the  host  for  a  period 
of  about  seven  days, 
becoming  quite  globu- 
lar and  much  enlarged. 

Under  favorable 
conditions  the  tick 
becomes  sexually  dif- 
ferentiated after  the 
fourth  molt,  requiring 
about  four  months  to 
reach  this  stage.  Others 
have  not  become  sex- 
ually differentiated  Fig.  22.3.  —  Shomng  egg  of  Ornithodorus  coriaceus  and 
wif  li  fi\'<i  mnlf  <s        Orrli  larvae  of  the  same  in  the  act  of  emerging  ;    also  two  fully 

Wltn  me  molts.      Urdl-  emerged  individuals.       X  14. 

narily   the   tick    molts 

once    for  each  engorgement,  but   there   may   be  two  molts  between 

feedings. 

Even  though  sexual  differentiation  is  accomplished  during  the  course 
of  one  summer,  there  seems  to  be  little  evidence  at  present  that  there 
is  more  than  one  generation  per  year. 

Fully  developed  adult  ticks  were  brought  into  the  laboratory 
September  21,  1913,  having  been  in  captivity  in  the  same  stage  four 
months  previous  and  w^ere  still  active  and  eager  to  bite  January  1, 
1915,   a  period   of  about  20    months.      No   molts  had   taken   place 


370       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


during  this  time,  notwithstanding  the  fact  that  full  engorgement  had 
occurred  repeatedly  and  many  eggs  had  been  deposited. 

Remedies  for  Tick  Bites.  —  For  the  bite  of  Omithodorus  mouhata, 
Wellman  (in  Ms.  according  to  Nuttall,  1908)  "  recommends  prolonged 
bathing  in  very  hot  water,  followed  by  the  application  of  a  strong 
solution  of  bicarbonate  of  soda,  which  is  allowed  to  dry  upon  the  skin. 
He  states  that  this  treatment  is  comforting.  For  severe  itching  he 
advises  smearing  the  bites  with  vaseline  which  is  slightly  impregnated 
with  camphor  or  menthol.  Medical  aid  should  be  sought  when  compli- 
cations arise." 

Scorpions 
Class  Arachnida,  Order  Scorpionida 

Characteristics  of  the  Scorpionida.  —  The  most  striking  characteris- 
tics of  the  scorpions  are,  first,  the  formidable  pedipalps  terminating  in 
strong  lobster-like  chelne  ;  second,  the  long  tail-like  postabdomen  termi- 
nating in  a  bulbous  sac  and  sting 
(Fig.  224).  "The  cephalothorax 
is  compact  and  unsegmented ;  the 
abdomen  is  broadly  joined  to  the 
thorax  .  .  .  consists  of  seven  seg- 
ments, and  a  slenderer  tail-like  divi- 
sion, the  postabdomen  or  cauda, 
consisting  of  five  segments.  .  .  . 
The  cephalothorax  bears  a  pair  of 
eyes  near  the  middle  line,  the  median 
eyes,  and  on  each  side  near  the 
cephalolateral  margin  a  group  of 
from  two  to  five,  the  lateral  eyes. 
A  few^  scorpions  are  blind.  .  .  . 
Scorpions  breathe  by  means  of 
book-lungs,  of  which  there  are  four 
pairs,  opening  on  the  lower  side  on 
the  third  to  the  sixth  abdominal 
segments.  .  .  .  The  sexes  of  scor- 
pions differ  in  that  the  male  has 
broader  pincers  and  a  longer  post- 
abdomen. Scorpions  do  not  lay 
eggs,  the  young  being  developed 
within  the  mother ;  after  the  birth 
of  the  young,  the  mother  carries 
them  about  with  her  for  some  time, 
attached  by  their  pincers  to  all  portions  of  her  body.  .  .  .  Scorpions 
live  in  warm  countries.  They  are  common  in  the  southern  portion  of 
the  Ignited  States,  but  are  not  found  in  the  North.     They  are  nocturnal. 


Fig.  224. 


-A  scorpion,  Hadrurus  hirsutus. 
X  .6. 


VENOMOUS  INSECTS  AND   ARACHNIDS  371 

remaining  concealed  during  the  day,  but  leaving  their  hiding  places  at 
dusk.  .  .  .  They  feed  upon  spiders  and  large  insects,  which  they  seize 
with  the  large  chelse  of  the  pedipalps  and  sting  to  death  with  their 
caudal  poison  sting"  (Comstock). 

The  order  Scorpionida  is  divided  into  six  families  of  which  there 
are  four  in  the  United  States,  separated  according  to  Comstock  (1912, 
loc.  cit.),  viz. : 

A.   Only  one  spur  at  the  base  of  the  last  tarsal  segment  of  tlie  last  pair  of  legs, 

and  this  is  on  the  outside Scorpionidce 

A  A.   One  or  two  spurs  on  each  side  at  the  base  of  the  last  tarsal  segment  of  the 
last  pair  of  legs. 
B.    From  three  to  five  lateral  ej'es  on  each  side. 

C.   Sternum  triangular;  usually  a  spine  under  the  sting     Buthidce 
CC.   The  lateral  margins  of  the  sternum  nearly  parallel;   sternum 
usually  broader  than  long;    no  spine  under  the  sting 

Vejovidoe 
BE.   Only  two  lateral  e.yes  on  each  side Chactidce 

Over  three  hundred  species  of  scorpions  are  known,  of  which  over 
sixty  occur  in  the  United  States,  of  which  the  following  are  characteris- 
tic: 

Isonietrus  maculatus  Linn.,  known  as  the  spotted  Isometrus,  is 
widely  distributed  in  tropical  and  sub-tropical  countries.  This  species 
is  described  by  Comstock  as  follows :  "A  dirty  yellow  species  marbled 
and  flecked  with  black.  The  body  is  thin  and  slender.  In  the  female 
the  postabdomen  is  usually  about  as  long  as  the  rest  of  the  body;  in 
the  male,  it  is  often  twice  as  long.  The  hand  is  long  and  thin,  thinner 
than  the  tibia  of  the  pedipalp ;  the  finger  is  from  one  and  a  half  to  two 
times  as  long  as  the  hand.  The  combs  ^  have  from  seventeen  to  nine- 
teen teeth.  The  female  grows  to  nearly  two  inches  in  length  ;  the  male 
to  nearly  three  inches. 

Centrums  carolhiianus  possesses  a  spine  or  tubercle  under  the  sting ; 
body  striped  with  black  and  yellow ;  a  small  pale  median  spot  on  the 
anterior  border  of  the  cephalothorax ;  legs  pale  yellow ;  postabdomen 
pale.     Occurs  in  the  Southern  states  (Comstock). 

Hadrurus  hirsutiis  Wood  is  a  very  large  and  hairy  species  found  in 
the  Southeast.  The  penultimate  tarsal  segment  of  the  first  three  pairs 
of  legs  is  furnished  with  long  hairs  on  the  back  (Comstock). 

Vejovis  carolinus,  a  reddish  brown  species,  occurs  from  South  Carolina 
to  Texas. 

Scorpion  Sting.  —  The  "aculeus"  or  sting  of  the  scorpion  is  located 
terminally  on  the  final  bulbous  segment.  The  bulbous  segment  in- 
closes a  venom-containing  vesicle  connected  with  the  sting  which 
terminates  in  a  hollow  needle-like  point.     The  sting  curves  downward 

1  The    combs    of  a   scorpion  are  located  ventrally,   origfinat  ing  from   the 
"selerite  on  the  middle  line  of  the  body"  just  anterior  to  the  first  segment  of 
the  postabdomen.     Each  comb,  of  which  there  are  two,  is  provided  with  so- 
called  teeth. 
2b 


372       MEDICAL  AND   VETERINARY  ENTOMOLOGY 


when  the  "tail"  is  extiended,  but  upwards  and  forwards  when  the  scor- 
pion poises  for  attack  or  defense,  the  entire  tail-like  postabdomen  being 
curved  dorsally  and  forwards.  The  victim  is  struck  quickly  and  re- 
peatedly, the  thrust  being  made  quite 
near  the  head  of  the  scorpion. 

Scorpion  stings  are  quite  common 
in  California ;  ordinarily  most  persons 
pay  no  more  attention  to  the  sting  of 
a  scorpion  than  to  the  sting  of  a  wasp. 
The  pain  produ(?ed  is  instant  and  quite 
penetrating.  In  some  instances  the 
wound  is  quite  severe  and  systemic 
disturbances  may. result.  Fatal  cases 
rarely  if  ever  occur. 

Treating  the  wound  promptly  with 
ammonia  ordinarily  brings  prompt 
relief. 


Whip  Scorpions 
Class  Arachnida,  Order  Pedipalpida 

Characteristics    of   Pedipalpida.  — 

The  Pedipalpida  resemble  scorpions 
in  some  respects  in  that  the  pedipalps 
are  similar.  The  first  pair  of  legs  is 
elongated  and  tactile,  while  the  last 
three  pairs  are  ambulatory.  The  term 
"whip  scorpion"  is  applied  to  the 
Family  Thelyphonidse,  because  the  ter- 
minal end  of  the  abdomen  is  provided 
with  a  long  slender  many-segmented 
appendage  (Fig.  225).  "Grampus" 
and  "vinegerone"  are  also  common 
names.  The  species  are  tropical  and 
subtropical. 

The  whip  scorpion,  Mastigoprodus 
giganteus,  occurs  in  southern  Califor- 
nia, mainly  in  sandy  desert  places 
where  it  burrow^s  in  the  sand  under 
debris.  They  are  commonly  regarded 
as  poisonous,  although  they  cannot  sting,  but  may  bite.  The  writer 
has  found  that  the  natives  invariably  fear  this  creature  very  consider- 
ably, but  knows  of  no  evidence  to  justify  this  attitude. 


Fig.  225. — Whip  scorpion    (Pedipal- 
pida) Mastigoproctus  giganteus.     X  .8. 


VENOMOUS   INSECTS  AND   ARACHNIDS 


373 


SOLPUGIDS 

Class  Arachnida,  Order  Solpugida 

Characteristics  of  the  Solpugida.  —  The  solpugids  are  characterized 
in  the  Cambridge  Natural  History  (Vol.  IV,  p.  423),  viz. :  "  Tracheate 
Arachnids,  with  the  last  three  segments  of  the  cephalothorax  free  and 
the  abdomen  segmented.  The  chelicerae  are  largely  developed  and  che- 
late, and  the  pedipalpi  are  leg-like,  possessing  terminal  sense  organs" 
(Fig.  226). 

The  general  appearance  is  spider-like ;  they  are  very  hairy,  largely 
nocturnal,  occurring  in  desert  tropical  regions.  Though  little  is  known 
about  this  interesting  group,  they  are 
fairly  common  in  certain  portions  of 
southern  California,  notably  in  the 
neighborhood  of  Salton  Sea,  where  they 
are  regarded  as  exceedingly  venomous. 
The  writer  has  been  told  that  the  pres- 
ence of  one  of  the  animals  in  a  watering 
trough  would  result  in  the  death  of  any 
animal  drinking  from  the  same.  There 
is  evidently  not  the  slightest  foundation 
for  this  belief.  Their  bite  is  benign. 
Common  names  applied  to  this  order 
are  "Sun  Spider"  and  "Wind  Scor- 
pion." 

The  order  is  represented  by  a  large 
number  of  species  occurring  only  in 
tropical  and  subtropical  countries,  notably  Africa.  There  are  said  to 
be  only  twelve  species  in  the  United  States,  all  but  one  belonging  to 
the  two  genera,  Eremobates  and  Ammotrecha. 


Fig.  226.  —  Sun  spider  (Solpugid), 
Eremobates  cinerea.      X  1- 


Centipedes 
Class  Myriapoda,  Order  Chilopoda 

Characteristics  of  Myriapoda.  —  The  Myriapoda  are  worm-like 
animals  with  separate  head,  possessing  antennae,  and  many  fairly  similar 
segments,  each  possessing  one  or  two  pairs  of  segmented  appendages. 
Like  the  insects  they  are  tracheated  and  for  the  most  part  terrestrial. 

The  class  Myriapoda  is  divided  into  four  or  five  orders  of  which  the 
following  are  well  known,  viz.:  Chilopoda,  the  centipedes,  with  only 
one  pair  of  appendages  to  each  segment ;  and  the  Chilognatha 
(Diplopoda),  the  Millipedes,  with  two  pairs  of  appendages  to  each 
segment,  e.g.  Julus  nemorensis,  a  so-called  "  thousand-legged  worm." 

Characteristics  of  Centipedes.  —  The  Chilopoda  have  only  one  pair 
of  appendages  to  each  segment  and  are  widely  separated  at  the  bases, 


374        MEDICAL  AND   VETERINARY    ENTOMOLOGY 


the  antennie  are  many  jointed,  the  genital  pore  is  located  on  the 
terminal  body  segment.  The  larger  species,  at  least,  are  carnivorous, 
feeding  mainly  on  insects.  Notwithstanding  the  confusing  abundance 
of  walking  appendages  the  centipedes  crawl  very  rapidly. 

Unlike  the  Millipedes,  which  possess  no  organs  of  defense  except 
glands  which  secrete  an  offensive  odor,  the  Centipedes  are  provided 
with  powerful  poison  claws  located  immediately  ven- 
tral to  the  mouth,  and  connected  by  means  of  a  hollow 
tube  with  large  poison  glands. 

The  larger  species  of  Centipedes  belong  to  the 
following  genera :  viz.,  Scolopendra,  Lithobius  and 
Geophilus,  and  may  be  over  six  inches  in  length, 
some  are  reported  to  be  eighteen  inches  long. 

Venomous  Centipedes.  —  The  larger  centipedes 
are  commonly  regarded  as  very  venomous,  and  it 
is  said  that  their  bite  may  be  fatal  to  man.  It  is 
true  that  an  insect  captured  by  Scolopendra  or 
Lithobius  is  killed  almost  instantly  when  the  poison 
claws  close  upon  it. 

In  southern  California  the  large  greenish  cen- 
tipede Scolopendra  hews  Girard  (Fig.  227)  is  greatly 
feared.  It  measures  from  four  to  five  inches  in 
length  and  has  a  very  formidable  appearance.  It 
is  said  that  it  not  only  punctures  the  skin  with  its 
^omous  centipede'  poisou  claws,  causiug  Considerable  pain,  but  also 
Scolopendra  heros.    produccs   a   "  rcddish    strcak  where    it    has   crawled 

X    66 

upon  the  body."  It  is  interesting  to  know  that 
these  animals  are  also  markedly  phosphorescent,  which  may  possibly 
account  for  some  of  the  phenomena  produced  on  the  skin,  Geophilus 
electricus  and  G.  phosphoreus  are  notable  examples  of  phosphorescent 
species. 


APPENDIX  I 
GENERAL  CLASSIFICATION  OF  BACTERIA  AND  PROTOZOA 

Differences  in  Methods  of  Study  in  Bacteria  and  Protozoa.  —  The 

lowest  forms  of  animal  life  belong  to  the  Protozoa,  while  the  lowest 
forms  of  vegetable  life  belong  to  the  Bacteria  in  a  broad  sense.  Since 
the  epoch-making  discoveries  of  Pasteur  and  Koch,  advancing  the 
"germ  theory"  of  disease,  these  organisms  have  been  the  objects  of 
research  in  many  lands  and  by  many  investigators,  and  distinct  sciences, 
namely,  Bacteriology  and  Protozoology,  have  been  developed.  The 
methods  of  study  in  the  two  branches  are  rather  different,  inasmuch  as 
Bacteria  may  be  studied  in  culture  media,  while  the  Protozoa  ordinarily 
require  different  methods,  i.e.  are  not  as  readily  amenable  to  culture 
media.  Calkins  has  stated  this  in  the  following  clear  terms :  "  The 
study  of  protozoa,  even  when  possible  to  apply  bacteriological  methods, 
is  fundamentally  different  from  the  study  of  bacteria,  as  at  present 
carried  on.  The  latter,  dependent  on  growth  conditions,  colony  forma- 
tion, reactions  to  media,  etc.  are  essentially  physiological,  and  based 
upon  the  function  of  the  organisms.  The  study  of  protozoa,  on  the 
other  hand,  is  essentially  morphological,  or  based  upon  the  structures 
of  the  protozoan  cell,  and  involves  the  changes  in  cell  structures  which 
an  individual  undergoes  during  various  phases  of  vitality.  Hence  it 
becomes  necessary  first  of  all  to  know  the  life  history  of  the  protozoon, 
and  the  fundamental  modification  which  its  protoplasm  assumes." 
The  student  of  Medical  Entomology  should  not  only  be  familiar  with 
general  structures  and  life  history  processes,  but  also  with  the  methods 
of  study  applied  in  the  laboratory  such  as  the  preparation  and  use  of 
culture  media,  animal  experimentation,  etc. 

The  Bacteria.  —  There  are  "  only  three  principal  types  of  bacteria, 
—  the  sphere,  the  rod  and  the  spiral.  Under  normal  and  uniform  condi- 
tions of  life  each  breeds  true,  the  spherical  producing  spheres  and  the 
rods,  again,  only  rods."  ^ 

Classification.  —  The  following  classification  after  Migula,^  adapted 
after  Jordan,  with  the  addition  of  examples  in  the  transmission  of  which 
insects  and  arachnids  are  concerned,  will  serve  as  a  general  guide  in 
locating  certain  diseases  touched  upon  in  the  preceding  chapters.     Un 
fortunately,  contrary  to  the  statements  made  above,  it  seems  necessary 

^  Jordan,  Edwin  O.,  1908.  Textbook  of  general  bacteriology,  557  pp. 
W.  B.  Saunders  Co. 

'^  Migula.     System  der  Bacterien,  Jena,  1897  (after  Jordan,  loc.  cit.). 

375 


376       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

to  resort  to  a  classification  based  on  structural,  instead  of  physiological, 
characters  (Fig.  228). 


o  a 


r^ 


^ 


Fig.  228.  —  Illustrating  types  of  bacteria.  A.  Sphere  or  coccus ;  B.  Rod  or  bacillus ; 
C.  Spiral  or  spirillum  ;  D.  Example  of  higher  bacteria.  (Adapted  in  part  after  Jordan. 
Greatly  enlarged.) 

I.   Cells  globose  in  a  free  state,  not  elongating  in  any  direction  before  division 

into  1,  2  or  3  planes 1.  Coccacea; 

II.   Cells  cylindrical,  longer  or  shorter  and  only  dividing  in  one  plane,  and 
elongating  to  about  twice  the  normal  length  before  the  division. 
a.  Cells  straight,  rod-shaped,  without  sheath,  non-motile,  or  motile  hy  means 

of  flagella 2.  Bacteriaceae 

h.  Cells  crooked,  without  sheath 3.  Spirillacese 

c.  Cells  inclosed  in  a  sheath 4.  Chlamj'^dobacteriacese 

1.  Coccacea? 
Cells  without  organs  of  motion 

a.  Division  in  one  plane Streptococcus 

e.g.  Streptococcus  erysipelatis  of  erysipelas 

b.  Division  m  two  planes Micrococcus 

e.g.  Micrococcus  melitensis  of  malta  fever 

c.  Division  in  three  planes Sarcina 

Cells  with  organs  of  motion 

a.  Division  in  two  planes Planococcv^ 

b.  Divisions  in  three  planes Planosarcina 

2.  Bacteriacea' 

Cells  without  organs  of  motion Bacterium 

Cells  with  organs  of  motion  (flagella) 

a.  Flagella  distributed  over  the  whole  body  .     .     .    Bacillus 
e.g.  Bacillus  anthracis  of  anthrax 
Bacillus  typhosus  of  typhoid 
Bacillus  pestis  of  bubonic  plague 
Bacillus  tuberculosis  of  tuberculosis 


APPENDIX  I  377 

b.  Flagella  polar 

3.  Spirillaceae 

CeUs  rigid,  not  snake-like  or  flexuous  Svirosoma 

a.  Cells  without  organs  of  motion    •     ■     •     •     •     '    '^^P^'^^soma 

b.  CeUs  with  organs  of  motion  (flagella)  Microsvira 

1.  Cellswithl,veryrarely2to3polarflagella     .     Mtcrospuu 

2    Cells  with  polar  flagella-tufts  .     .     •     •     •     •  ^V^nuum 

ea   Spirillum  (_vibris)cholercBoiAs\&tic  cholera  ^   .     ,    ,„ 

CeUs  flexuous  (see  also  under  Protozoa).  ,    •     •     •  SpiroMa 

e.g.  Spirochceta  duttoni  of  African  relapsing  fever 

4.  Chlamydobacteriaceaj  (higher  bacteria) 
Cell  contents  without  granules  of  sulphur 

a.  Cell  threads  unbranched.  Qir^^tnihrir 

\  Slls  surrounded   by   a  very  delicate,   -rcely^;;^!^^^^^^^^^^ 

2.  Sheathdearly  visible  (freshwater)   .     .     •     •     C;WAm 

6.  CeU  threads  branched     .     •     • rSIrS 

Cell  contents  containing  sulphur  granules iniomrix 

The  Protozoa 

Classification  of  the  Protozoa}  .      ,    ,^-     ■^^ 

Phvlum  Protozoa ;  Unicellular  animals  (J^ig.  i) 

Subphylum  Mastigophora.     Flagella-bearing  protozoa 
Class  zoomastigophora.     Undisputed  animal  flagellates 
Subclass  Lissoflagellata  without  protoplasmic  collars 

..j'^tfrSf  £ni  of  African  relapsing  fever,  carried  by  a  tick, 

Ornithodorus  moubata  .      ,     ,     .  •  j  u     „  +;<,!. 

e.g.  Spirocha^ta  gallinarwn  of  poultry  spirocha-tosis,  carried  by  a  tick, 

Argas  persicus 
e.g.  Treponema  pallidurn  of  Syphilis 

e.g^'nypJZloZ^l^nb^^^   of  African  sleeping  sickness,  carried  by  a 

Tsetse  flv.  Glossina  palpalis  . 

eq    Trypanosoma  brucei  of  Nagana  (disease  of.certam  African  beasts 

of  burden),  carried  by  a  Tsetse  fly,  Glossina  morsitans 
Subclass  Choanoflagellata.    With  protoplasmic  collar   ^ 
(No  pathogenic  species) 
Class  Phytomastigophora.    With  plant  characteristics 
(No  pathogenic  species)  ,       j-        i 

Subphylum  Sarcodina.     Protozoa  with  pseudopodia  only 
Class  Rhizopoda.     Pseudopodia  without  axial  filaments 
Subclass  Amoebsea.    With  firm  lobose  pseudopodia 

Order  Gymnamcebia 
e  a.  Entamoeba  histohjtica  of  tropical  dysentery 
Class  Actinopoda.    With  supporting  axial  filaments 

(No  pathogenic  species)  . 

Subphylum  Infusoria.    Motile  organs,  cilia ;  dimorphic  nuclei 
Class  Ciliata.    Without  tentacles ;  always  ciliated 
Order  Holotrichida 

1  Adapted  after  Calkins,  including  only  groups  of  pathogenic  importance. 


378       MEDICAL  AND   VETERINARY  ENTOMOLOGY 

e.g.  Balantidium  coli;   causative  organism  of  a  type  of  dysentery  known 

as  Balantidiosis 
Class  Suctoria.     With  suctorial  tentacles ;  embryos  ciliated 
(No  pathogenic  species) 
Subphylum  Sporozoa.     No  motile  organs ;  reproducing  by  spores 
Class  Telosporidia.     Reproduction  ends  life  of  cell 
Subclass  Gregarinida.     Lumen-dwelling  sporozoa 

Order  Schizogregarinida 
e.g.  Ophnjocystis 

Order  Eugregarinida 
e.g.  Monocyslis 
Subclass  Coocidiidia.     Cell-dwelling  sporozoa 

Order  Tetrasporocystida 
e.g.  Coccidium  tenellum  ( ?)  of  Blackhead  in  turkeys 
Subclass  Hsemosporidia.     Sporozoan  parasites  of  the  blood 

Order  Ha?mosporida 
e.g.  Hcemamoeba  {Proteosoma)  relida  of  bird  malaria  in  sparrows;    in 
India  carried  by  Culicine  mosquitoes 
Order  Xenosporida 
e.g.  Plasmodium  vivax  of  tertian  malaria,  carried  by  certain  Anopheline 

mosquitoes 
e.g.  Babesia  higemina  of  Texas  cattle  fever,  carried  by  a  tick,  Mar- 

garopus  annulatus 
e.g.  Piroplasma  hominis  (doubtful  or  disproven)  of  Rockj^  Mountain 
spotted  fever  of  human  beings,  carried  by  a  tick,  Dermacentor 
venustus 
Class  Neosporidia.     Reproduction  with  continued  life  of  cell 
Subclass  Myxosporidia.     Spores  with  distinct  capsules 

Order  Mj^xosporida 
e.g.  Myxoboliis  cyprini  of  pox  disease  of  the  carp 

Order  Microsporida 
e.g.  Nosema  bombycis,  causative  organism  of  pebrine  in  silkworms 


INDEX 


Aeanthiidae,  69,  353. 
Aeariasis,  330. 

psoroptic,  337. 

sarcoptic,  330. 
Aearina,  296,  330. 
Aearus  muscarum,  197. 
Achorion  sehoenleini,  62. 
Aculeate  hymenoptera,  358. 
"Adobe"  tick,  323. 
iEdes  calopus,  3,  35,  88,  92,  114,  117. 
^des  (genus),  100. 
iEdinae,  86,  97,  99. 
iBdini,  87. 
^domyia,  100. 
African  coast  fever,  313. ' 

relapsing  fever,  327. 

relapsing  fever  tick,  326. 

relapsing  fever  tick  control,  328. 

sleeping  sickness,  8,  34,  210. 

sleeping  sickness  control,  213. 

sleeping  sickness  reservoirs,  212. 

sleeping  sickness  transmission,  212. 
Agramonte,  113. 
Aldrichia,  98. 
Alpine  scurvy,  145. 
Amblycera,  53. 
Amblyomma    americanum,    301,    316, 

321. 
Amblyomma  (genus),  323. 
American  roach,  39. 
Ammonia,  for  cone-nose  bite,  79. 
Ammotrecha,  373. 
Amoebic  dysentery,  8. 
Anarsia  lineatella,  348. 
Anatomy,  insect,  13. 

external,  19. 

internal,  14. 
Anderson,  J.  F.,  and  Frost,  W.  H.,  224. 
Andre,  Charles,  181. 
Angoumois  grain  moth,  348. 
Ankylostoma  eaninum,  183. 
Ankylostoma  duodenale,  8,  9. 
Annelida,  10. 
Anopheles  (genus),  2,  5,  87,  88,  97,  98. 

aitkeni,  99. 

albimanus,  112. 

algeriensis,  98. 

arabiensis,  98. 

argyrotarsus,  112. 

barberi,  98. 

bifurcatus,  98. 

claviger,  104. 


control  of,  120. 

corethroides,  98. 

crucians,  89,  98,  112. 

dthali,  98. 

eiseni,  98. 

franciscanus,  98. 

gigas,  98. 

immaculatus,  99. 

lindsayi,  99. 

maculipennis,  11,  98,  112. 

nigripes,  99. 

pseudopunctipennis,  98. 

punctipennis,  98,  112. 

quadrimaculatus,  112. 

smithi,  99. 

welcomei,  98. 

wing  of,  81. 
Anopheline     characteristics    (see  Mos- 
quitoes) 
Anophelini,  86,  88. 
Anthomyia  radicum,  241,  242. 
Anthomyidae,  241,  263. 
Anthonomus  grandis,  348. 
Anthrax,  34,  35,  46,  72,  145,  151. 
Anthrenus  museorum,  46. 

scrophulariae,  46. 

verbasci,  46. 
Ant  Uon,  21. 

mouth  parts  of,  32. 
Ants,  stinging,  358. 

velvet,  358. 
Apatolestes,  156. 
Aphaniptera,  273. 
Aphis  lions,  mouth  parts  of,  32. 
Apidffi,  359. 

Apiomerus  crassipes,  77. 
Apis  mellifera,  353,  359. 

mouth  parts  of,  31. 

sting  of,  353. 
Aptera,  16,  18,  19. 
Arachnida,  12,  296,  330. 
Arachnid  venoms,  351. 
Aradidae,  69. 
Araneida,  359. 
Argas  americanus,  323. 

brumpti,  326. 

cucumerinus,  326. 

miniatus,  323. 

reflexus,  326. 

vespertilUonis,  326. 
Argas  persicus,  3,  323,  365. 

control  of,  326. 


379 


380 


INDEX 


Argas  persieus,  damage  done,  325. 

description  of,  323. 

life  history  of,  324. 

relation  to  spirochsetosis,  325. 
ArgasidsB,  298. 
Armigeres,  99. 
Arribalzagia,  97. 
Arsenical  dips  for  ticks,  309. 
Arthropoda,  10. 
Asearis  canis,  183. 

lumbricoides,  8. 
Asiatic  cholera,  181. 
Assassin  bugs,  75. 
Asturian  leprosy,  145. 
Atoxyl,  against  fly  larvae,  195. 
Attagenus  peUio,  47. 
Auchmeromyia  luteola,  239. 
Australian  roach,  39. 
Avicularia  ealifornicus,  364. 
Aviculariidse,  364. 

Babesia  bigemina,  34,  305,  306. 

caballi,  320. 

canis,  320. 

ovis,  320. 
Bacillus  anthracis,  34,  47,  72,  145,  151. 

dysenteriae,  179. 

ieteroides,  114. 

pestis,  33,  278. 

prodigeosus,  174. 

pyocyaneus  aureus,  41. 

tuberculosis,  33,  180. 

typhosus,  177. 
Baeot,  A.  W.,  283. 
Bacteria,  classification  of,  375. 
Balantidium  coli,  9. 
Balfour,  A.,  326. 
Banks,  Nathan,  273,  317,  330. 
Bartonia  bacilliformis,  117. 

bodies,  117. 
Bass,  C.  C,  102,  110. 
Bats,  in  mosquito  control,  132. 
Bedbugs,  7,  11,  69,  353. 

bites  of,  72. 

China,  77. 

control  of,  73. 

disease  transmission  by,  72. 

habits  and  life  history  of,  71. 

how  distributed,  71.    • 

mouth  parts  of,  32. 

of  bat,  70. 

of  poultry,  70. 

of  swallow,  70. 
Bees,  32. 
Bee  sting,  353. 
Beetles,  22. 

bUster,  49. 

carpet,  46. 

carrion,  46. 

grain,  48. 

larder,  46.  ■ 

May,  47. 

mouth  parts  of,  32. 


relation  to  disease,  46. 

rove,  45. 

scavenger,  45. 

sexton,  46. 
Benzine  for  bedbugs,  73. 

for  body  louse,  67. 
Bignami,  A.,  102. 
Bird  Uce,  52. 
Bironella,  98. 

Bishopp,  C.  F.,  221,  228,  317,  318. 
Biting  hce,  21,  52. 

classification  of,  52. 

control  of,  57. 

damage  done,  53. 

habits  and  life  history,  52. 

mouth  parts  of,  32. 

of  angora  goat,  54. 

of  cat,  54. 

of  cattle,  54. 

of  deer,  55. 

of  dog,  54,  65. 

of  duck,  55,  57. 

of  goat,  54. 

of  goose,  55,  57. 

of  guinea  pig,  57. 

of  hen,  55,  57. 

of  horse,  54. 

of  pigeon,  56. 

of  swan,  56,  57. 

of  turkey,  55. 
Black  fly,  148. 
Blaizot,  L.,  64. 
Blatella  germanica   (see  Croton  bug), 

39. 
Blatta  orientaUs,  39.  * 

as  carrier  of  filaria,  43. 
Blepharoplast,  209. 
Blister  beetles,  49,  351,  352. 
Blow  fly,  237. 
Bluebottle  fly,  237. 
Blue  ointment  for  pubic  louse,  67. 
Blue,  Rupert,  281. 
BolUnger,  O.,  152. 
Bombidaj,  359. 
Book  louse,  8,  21. 

mouth  parts  of,  32. 
Boophilus  (genus),  323. 

australis,  308. 

bovis,  300,  307. 

deeoloratus,  308. 
Borax,  for  cockroaches,  44. 

for  fly  larvae,  195. 

lotion,  67. 
Botflies,  7,  13,  246. 

of  cattle  (see  Hypoderma  lineata). 

of  deer,  257. 

of  horse  (see  Gastrophilus  equi). 

of  humans,  258. 

of  rodents,  257. 

red-tailed,  250. 
Bothriocyrtus  ealifornicus,  364. 
Bouton,  31. 
Bovine  scabies,  343.  , 


INDEX 


381 


Braehiomyia,  99. 
Braun,  M.,  6,  49,  332. 
Breakbone  fever,  117. 
Breathing  system,  tracheal,  13. 
Brill's  disease,  64. 
Bristletails,  mouth  parts  of,  32. 
Brown-tail  moth,  351. 
Bruce,  D.,  210. 
Brumpt,  B.,  65,  79. 
Buboes,  33,  278. 
Bubonic  plague,  2,  33,  278. 
Buffalo  gnats,  143,  147. 

bites  of,  145. 

breeding  habits,  144. 

classification  of,  147. 

control  of,  147. 

larvae  of,  143. 

pupae  of,  144. 

relation  to  disease,  145. 
Bugs,  22. 

Buhach  (see  Pyrethrum). 
Bumblebees,  359. 
Buthidse,  371. 
Butterflies,  22. 

mouth  parts  of,  31,  32. 

Caddis  flies,  22. 

mouth  parts  of,  32. 
Caeca,  gastric,  15. 
Calhphora  erythrocephala,  237,  262. 

vomitoria,  237. 
Calmette,  351. 
Campodea,  16. 
Cantharidae,  352. 
Cantharidin,  49. 
Carassius  auratus,  133. 
CarboUc  acid  for  fly  larvae,  195. 

for  myiasis,  240. 
Carbon  bisulphide  for  bots,  249. 

for  squirrels,  287. 
Carbuncle,  152. 
Cardo,  25. 
Carlet,  G.,  355. 
Carrion's  disease,  117. 
Carroll,  James,  95,  113. 
Cassa,  J.  LeR.  Y,  140. 
Cassia,  oil  of,  132. 
Castellani,  A.,  182,  210. 
Castor  bean  tick,  321. 
Caterpillars,  14. 
Cattini,  J.,  181. 
CelUa,  97,  112. 

argjrrotarsis,  112. 
Centipedes,  11,  373. 
Centriu-us  carolinianus,  371. 
Cephenomyia,  257. 
Ceratitis  capitata,  264. 
Ceratophyllus   acutus,   269,   276,   283, 
284. 

fasciatus,  7,  65,  270,  276. 

londinensis,  277. 

niger,  276. 
Cestoda,  7,  9. 


Cetonia  aurata,  48. 

Chactidae,  371. 

Chaetopoda,  10. 

Chagas,  C.,  79. 

Cha'gas  diseas?,  79. 

Chagasia,  98. 

Chandler,  W.  L.,  365. 

Charbon,  152. 

Cheshire,  F.  R.,  353. 

Chevril,  R.,  243. 

Chiggers,  345. 

Chigoe,  247,  248,  291. 

Chilognatha,  373. 

Chilopoda,  373. 

Chinese  bedbug,  77,  353. 

Chin  fly,  250. 

Chironomidae,  81. 

Chlorine,  for  chicken  dip,  58. 

Chloronaphtholeum  for  lice,  68. 

for  equine  mange,  334. 

for  fly  larvae,  195. 

for  mosquitoes,  126. 

for  myiasis,  240. 

for  sheep  dip,  295. 

for  sheep  scab,  343. 
Cholera,  Asiatic,  181. 

fly,  197. 
Chowning,  W.  M.  (Wilson,  L.  B.,  and), 

315. 
Chi'istya,  97. 

Christophers,  S.  R.  (see  Stephens). 
Chrysanthemum  cinerariafolium,  197. 
Chrysomyia  maeellaria,  6,  13,  234,  263. 
Chrysops,  156. 
Chub,  Sacramento,  133. 
Cicada,  mouth  parts  of,  32. 

killer,  359. 
Cimex  hemipterus,  70,  73. 

lectularius  (see  also  Bedbug),  70,  73, 
279. 

macrocephalus,  70. 

pilosellus,  70. 

pipestrelli,  70. 

rotundatus,  70. 
Cimieidae,  69. 
Cinchona,  102. 
Citellus  beecheyi,  283. 
Citronella,  oil  of,  4,  131. 
Classification  of  insects,  15. 
Clypeus,  25. 
Cnemidocoptes  gallinae,  336. 

mutans,  335. 
Coast  fever,  African,  313. 
Coccidium  oviforme,  9. 
Cockchafers,  47. 
Cockroach,  control  of,  44. 

disease  transmission  by,  40. 

distribution  of,  39. 

habits  and  life  history  of,  37. 

mouth  parts  of,  32. 

species,  39. 
Coenurus  cerebralis,  256. 
Cole,  L.  J.,  171. 


382 


INDEX 


Coleoptera,  22,  32. 

larvae  of,  13. 
Columbacz  midge,  149. 
Commensalism,  6,  8. 
Compsomjna  macellaria,  234. 
Comstoek,  J.  H.,  353,  359,  363,  371. 
Comstock,  J.  H.  (Needham,  J.  G.,  and), 

17. 
Conev noses,  11,  32,  75,  352. 

bites  of,  77. 

control  of,  79. 

life  history  of,  78. 

treatment  for  bite,  79. 
Congo  floor  maggot,  239. 
Conorhinus  protractus,  11,  77,  353. 
life  history  of,  78. 

megistus,  79. 

sanguisuga,  76,  352. 
Conseil,  F.,  64. 
Copeman,  S.  M.,  169. 
Copper  sulphate,  125. 
Cordylobia  anthropophaga,  238. 
Corethra,  81. 
Corethrinse,  81. 
Corrodentia,  8,  21,  32. 
Corrosive  sublimate  for  cone-nose  bites, 

79. 
Corsair,  two-spotted,  77. 
Cotalpa  lanigera,  48. 
Cotton-boll  weevil,  348. 
Cotton,  E.  C,  303. 
"CowkiUer,"  359. 
Craneflies,  80. 
Crawford,  J.,  177. 
Crayfish,  10. 
Creolin,  for  fly  larvae,  195. 

for  head  louse,  66. 

for  hen  flea,  293. 

for  lice  on  animals,  68. 

for  mange,  335. 

for  myiasis,  240. 
Creophilus,  46. 
Cresyl,  for  mosquitoes,  132. 
Crickets,  19. 
Cropi(of  insect),  14. 
Eon  bug,  39. 

as  carrier  of  bacteria,  41. 

life  history  and  habits,  39. 
Crustacea,  10,  11. 
Ctenocephalus  canis,  6,  270,  275. 

felis,  275. 

muscuU,  270,  274. 

serratieeps,  275. 
Ctenopsyllidae,  273,  274. 
Cucujidae,  48. 
Culex,  characters,  84,  89,  99. 

fasciatus,  114. 

fatigans,  116. 

malariae,  104. 

penicillaris,  104. 

pipiens,  104,  131. 

pungens,  83. 

quinquefasciatus,  116,  117. 


Culicidae  (characteristics),  80. 

Culicinae,  97,  99. 

Culicini,  86. 

Culiseta  incidens,  83,  88. 

Cuterebra  cuniculi,  257. 

emaseulator,  257. 
Cyanide  fumigation,  74. 
Cyanide,  sodium  for  fly  larvae,  195. 
Cyelolepteron,  97. 
Cyprinodon  dispar,  134. 
Cysticercus  trichodectes,  65. 

Dacus  oleae,  264. 

Damsel  flies,  mouth  parts  of,  32. 

Darling,  G.  T.,  126. 

Datura  stramonium,  132,  197. 

Davidson,  A.,  78. 

Deaderick,  W.  H.,  107. 

Deinokerides,  99. 

Delphinium,  66,  67. 

Demodecidae,  344. 

Demodex  folliculorum,  344. 

var.  bovis,  345. 

var.  canis,  345. 

var.  hominis,  345. 

var.  suis,  345. 
Dengue,  117. 
Depluming  mites,  336. 
Dermacentor  (characteristics),  322. 

electus,  303. 

marginatus,  316. 

occidentaUs,  321,  365. 

reticulatus,  320. 

variabilis,  7,  316,  321,  365. 

venustus  {see  Tick  of  spotted  fever), 
317. 
Dermanyssidae,  346. 
Dermanyssus  gaUinae,  3,  12,  347. 

control  of,  347. 

damage  done,  347. 

habits,  347. 
Dermatitis,  348. 
Dermatobia  cyaniventris,  258. 

hominis  (see  Warble),  258. 

noxiaUs,  258. 
Dermestes  lardarius,  46. 

vulpinus,  46. 
Dermestidae,  46. 
Dewevre,  62. 
Diachloris,  156. 
Diarrhea,  summer,  179. 
Dibotlu-iocephalus  latus,  183. 
Digestive  system  of  insects,  14. 
Dip,  kerosene  for  horn  fly,  231. 

lime  and  sulphur,  339. 

for  bovine  scabies,  343. 

for  sheep  scabies,  339. 

for  swine  mange,  332. 
Diplococcus  pemphigi  contagiosi,  62. 
Diplopoda,  373. 
Dipping  for  horn  flies,  231. 

for  ticks,  308. 
Dipping  cattle,  343. 


INDEX 


383 


Dipping,  sheep,  341. 

swine,  332. 
Diptera,  22. 

Dipteron  type  of  mouth  parts,  28,  32. 
Dipterous  larvae,  13. 
Dipylidium  caninuni,  9,  65,  183. 
Disease,  causation  by  insects,  35. 

transmission  by  insects,  34. 
Distomum  americanum,  9. 
Di.xidae,  82. 
Doane,  R.  W.,  141. 
Dobson  flies,  21. 

larvse  of,  14. 

mouth  parts  of,  32. 
Docophorus  cygni,  56 

ieterodes,  55. 
Dog  tick,  303. 
Dragon  flies,  21,  132. 

mouth  parts  of,  32. 
Drepanidotaenia  infundibuliformis,  9. 
Drone  fly,  244. 
Dumdum  fever,  72. 
Dutton,  J.  E.,  210. 

Dutton,  J.  E.  (Todd,  J.  L.,  and),  327. 
Dysentery,  3,  179. 

amoebic,  9. 

Earthworms,  10. 
Earwigs,  19. 

mouth  parts  of,  32. 
Eehidophaga   gallinacea,   8,   274,    278, 

292. 
Echinorhychus  gigas,  47. 
Economic  losses  due  to  certain  insects,  3. 
Ectoparasites,  6. 
Elephantiasis,  115. 
Empusa  muscse,  197. 
Entamoeba  histolytica,  8,  179. 
Entoparasites,  6. 
Ephemerida,  21,  32. 
Epipharynx,  25. 
Equine  mange,  333. 
Eretmapodites,  99. 
Eremobates,  373. 
Eristalis  tenax,  244. 
Esten,  W.  M.  (Mason,  C.  J.,  and),  42, 

175. 
Eucalyptus,  132. 
Euplexoptera,  19,  32. 
Euproctes  chrysorrhea,  351. 
Euthrips  pjrri,  51. 

striatus,  51. 

tritici,  51. 
Eurypelma  hentzii,  364. 
Evans,  W.  J.,  210. 
External  parasitism,  36. 

Facultative  parasites,  6. 
Faichnie,  M.,  179. 
False  gid,  255. 
Fannia  canicularis,  241. 

in  urinary  tract,  243. 

sealaris,  241,  242. 


Fasciola  hepatica,  9. 
Favus,  62. 

Felt,  E.  P.,  45,  185,  285. 
Feltinella,  97. 
Ficker,  M.,  179. 
Filaria  bancrofti,  115. 

rytipleuritis,  43. 

sanguinus  hominis,  115. 
Filariasis,  115. 
Fiulay,  C,  113. 
Firth,  R.  H.  (Horrocks,  W.  M.,  and), 

179. 
Fishberry,  for  pubic  louse,  67. 
Fish  in  mosquito  control,  132. 
Fleas,  6,  22,  32,  266,  353. 

characteristics  of,  266. 

classiflcation  of,  273. 

control  of,  284. 

hosts  of,  270. 

life  history  of,  267. 

light  reactions  of,  273. 

longevity  of,  270. 

mouth  parts  of,  32,  281. 

of  cat,  275. 

of  dog,  270,  275. 

of  hen,  8,  278,  292. 

of  human,  270,  275. 

of  mouse,  270. 

of  rat,  270,  276. 

of  squirrel,  270,  276. 

plague  transmission  bv,  282. 
Flesh  flies,  233. 

adult  characteristics,  233. 

larval  characteristics,  233. 
Fletcher,  J.,  230. 
Flexner,  S.,  222. 
FUes,  bot,  246. 

caddis,  22. 

dragon,  21. 

flesh,  233. 

forest,  293. 

gad,  149. 

horse,  149. 

house,  22,  160. 

May,  21. 

papatici,  82. 

scorpion,  22. 

stone,  21. 

warble,  251. 
Floor  maggot,  239. 
Fly  cholera,  197. 

fungus,  197. 

poisons,  196. 

traps,  192. 
FoUicle  mites,  344. 
Follicular  mange,  344. 
Food  ordinance,  205. 
Force,  J.  N.,  204. 
Forest  flies,  293. 
Formaldehyde,  for  flies,  196. 
Formic  acid,  351. 
Formicidae,  358. 
Formicina,  358. 


384 


INDEX 


Fowl  tick  {see  Argas  persicus). 

FrambcBsia,  181. 

Francis,  M.,  240. 

Frisbie,  E.  F.,  353. 

Frost,  W.  H.,  222. 

Frost,  W.  H.  (Anderson,  J.  F.,and),  224. 

Fuchs,  C,  363. 

Fumigation,  for  bedbugs,  73. 

for  lice,  68. 

with  carbon  bisulphide,  287. 

with  hydrocyanic  acid  gas,  74. 

with  sulphur,  75. 
Fundulus,  134. 

Gadflies,  149. 
Galea,  25. 
Galeb,  O.,  43. 
GaU  flies,  22. 
Gamasidae,  346. 
Gamasoidea,  346. 
Gambusia  affinis,  133. 
Gametes  of  malaria,  111. 
Gametocytes  of  malaria,  110. 
Garbage  cans,  190. 

disposal,  191. 
Garmen,  H.,  146. 
Gasoline  for  bedbugs,  73. 

for  body  louse,  67. 
Gastric  caeca,  15. 

myiasis,  243. 
Gastrophilus  equi,  7,  246. 
life  history  of,  247. 
pathogenesis,  248. 
prevention,  249. 
treatment,  249. 

haemorrhoidalis,  249. 

nasalis,  250. 

peeuarum,  250. 
Geophilus  electricus,  374. 

phosphoreus,  374. 
Gerlach,  A.  C,  332. 
Gid,  256. 

false,  256. 
Giles,  G.  M.,  95. 
Giltner,  H.  A.,  117. 
Gizzard  (insect),  14. 
Glossina  flies  (see  Tsetse  flies). 

fusca,  212,  215. 

longipalpis,  215. 

longipennis,  215. 

morsitans,  211,  214. 

pallicera,  215. 

pallidipes,  215. 

palpalis,  211,  212,  214. 

var.  wellmani,  212,  214. 
Gnats,  buffalo  (see  Buffalo  gnats),  143. 

black,  148. 

classification  of,  147. 

control  of,  147. 

columbacz,  149. 

turkey,  148. 
Goldberger,  J.  (Shamberg,  J.  F.,  and), 
349. 


Goldfish,  in  mosquito  control,  133. 
Golgi,  C,  102. 

cycle  of,  108. 
Goriiocotes  abdominalis,  55. 

compar,  56. 

hologaster,  55. 
Goniodes  damicornis,  56. 

stylifer,  55. 
Goniops,  156. 
r.raells,  F.,  362. 
Grain  beetles,  saw-toothed,  48. 
Grampus,  372. 

Grasshopper,  mouth  parts,  25,  32. 
Grassi,  B.,  102,  104. 
Graybill,  H.  W.,  298,  302,  308. 
Greenbottle  fly,  238. 
Crround  squirrels,  283. 
Grub  in  the  head,  255. 
Grubs,  13. 

Gunpowder,  for  roaches,  45. 
Gypsum,  as  an  insecticide,  195. 
Gyropidae,  53. 

species  of,  57. 
Gyropus  graciUs,  57. 

ovalis,  57. 

Hadrurus  hirsutus,  12,  371. 
Haemagogus,  100. 
Haemamoeba  malariae,  108. 

praeeox,  106. 

vivax,  107. 
Hsemaphysalis,  322. 

leachi,  320. 

leporis,  321. 

palustris,  321. 
Haematobia  serrata  {see  Horn  fly). 
Haematopinus  acanthopus,  62. 

asini,  61. 

eurysternus,  61. 

hesperomydis,  62. 

macrocephalus,  61. 

pedalis,  61. 

piliferus,  61. 

spinulosis,  62,  65. 

suturaUs,  62. 

suis,  61. 

vituli,  61. 
Haematopota,  156. 
Haematosiphon  inodorus,  70. 
Halteres,  17. 
Harvest  mites,  345. 

treatment  for,  346. 
Haushalter,  and  Spillman,  180. 
Haustellata,  24. 

Head  maggot  of  sheep,  255,  265. 
characteristics  of,  255. 
life  history  of,  255. 
prevention  of,  257. 
symptoms  of,  256. 
treatment  of,  257. 

of  deer,  257. 
Heel  fly,  251. 
Heim,  F.,  47. 


INDEX 


385 


Hellebore  for  fly  larvae,  195. 
Helminthes,  7. 
Hemiptera,  7,  22,  69. 

heteroptera,  17,  69. 

homoptera,  17. 

parasita,  17. 

mouth  parts  of,  28,  32. 

wings  of,  17. 
Heterandria  formosa,  133. 
Heteropodg,,  360. 
Hewitt,  S.  G.,  160. 
HiU,  J.  H.,  222. 
Hine,  J.  S.,  156,  234. 
Hippobosea  equina,  295. 
Hippoboscidae,  293. 
Hirudinea,  10. 
Hirudo  medieinalis,  10. 
Histeridse,  46. 
Hodge,  C.  F.,  166,  190. 
Homalomyia  canieularis,  241. 
larva  of,  263. 

scalaris,  241. 
larva  of,  263. 
Homoptera,  69. 
Honeybee,  353. 

lateral  appendages  of,  355. 

morphology  of,  354. 

operation  of,  356. 

sting  of,  353. 
in  situ,  357. 

venom  sac  and  glands,  355. 
Hookworm  of  man,  8,  9. 
Hooker,  W.  A.,  328. 
Hoplopsyllus,  273. 

anomalus,  278,  283. 
Horn  fly,  3,  228. 

characteristics  of,  229. 

control  of,  230. 

damage  done,  230. 

larvae  of,  262. 

life  history  of,  229. 
Horrocks,  W.  M.   (Firth,  R.  H., 

179. 
Horseflies,  7,  149. 

autumn,  158.  ' 

bites  of,  151. 

black,  156. 

black  and  white,  157. 

breeding  habits  of,  149. 

classification  of,  155. . 

control  of,  155. 

green-headed,  157. 

larvae  of,  149. 

lined,  158. 

mouth  parts  of,  29,  32. 

relation  to  anthrax,  151. 

relation  to  surra,  152. 
Horvath,  G.,  69. 
House  fly,  160. 

breeding  habits,  163,  167. 

campaigns  against,  198. 

carrier  of  helminth  ova,  182. 

control  of,  184. 


and). 


description  of,  160. 

distribution  of  sexes,  161. 

economic  considerations,  171. 

influence  of  temperature  on,  166. 

larvae  of,  262. 

longevity  of,  169. 

mouth  parts  of,  31,  32. 

natural  enemies  of,  197. 

ordinances  against,  199. 

range  of  flight,  169. 

relation  to  disease,  171. 

relation  to  light,  170. 
Howard,  L.  O.,  3,  76,  78,  83,  94,  95, 
102,    131,    133,    155,    165,    171, 
179,  180,  182,  197,  201,  361. 
Howe,  L.,  182. 
Hunter,  W.  D.,  317. 
Hyalomma,  323. 

Hydrocyanic  acid  gas  fumigation,  74. 
Hymenolepis  diminuta,  183. 

nana,  183. 
Hymenoptera,  22,  358. 

mouth  parts  of,  31,  32. 
Hypoderma  hneata  {see  Warble  fly). 

bovis,  252. 
Hypopharynx,  27. 
Hypopus,  349. 

Ichneumon  flies,  22. 
Imago  (stage),  19. 
Impetigo,  62. 
Infantile  paralysis,  221. 
Infection,  direct,  35. 

indirect,  35. 

septicaemic,  35. 
Infusoria,  9. 
Insect  anatomy,  13. 

classification,  15. 

larvae,  13. 

venoms,  351. 

wings,  15. 
Insecta,  11. 

Insecticides  on  manure,  193. 
Insects,  disease  transmission  by,  34. 

disease  causation  by,  35. 

venomous,  351,  352. 
Intermittent  parasites,  7. 
Internal  parasitism,  36. 
Intestinal  myiasis,  243. 
Iodine,  tincture  of,   for  follicle  mites, 

345. 
Iron  sulphate  against  fly  larvae,  195. 
Irrigation  as  affecting  mosquito  control, 

128. 
Ischnocera,  53. 

Ischnoptera  pennsylvanica,  39. 
Isometrus  maculatus,  371. 
Isoptera,  21,  32. 
Isosoma  tritici,  348. 
Itch,  331. 

treatment  of,  332. 

grocers',  349. 
Ixodes,  322. 


386 


INDEX 


Ixodes  rieinus,  298,  301,  321,  365. 

var.  calif ornicus,  321. 
Ixodoidea,  296,  298. 

Jackson,  D.  D.,  178. 

Jail  fever,  64. 

Janthinosoma,  99. 

Jepson,  F.  P.  (Nuttall,  G.  H.  F.,  and), 

182. 
Jigger  flea,  274,  278,  291. 
Jiggers,  345. 
Jimson  weed,  132,  197. 
Joint-worm  of  wheat,  348. 
Jordan,  E.  O.,  177,  180. 
Julus  nemorensis,  373. 

Kala  azar,  72. 
KeUogg,  V.  L.,  39,  55. 

Kerosene,  for  body  louse,  67. 

for  bedbugs,  73. 

for  fowl  tick,  326. 

for  head  louse,  66. 

for  manure,  194. 

for  poultry  mite,  347. 

for  pubic  louse,  67. 

for  scaly  leg,  336. 
Kerteszia,  98. 
Kilbourne,  F.  L.,  305,  306. 
KiUifishes  in  mosquito  control,  134. 
King,  A.  F.  A.,  102. 
Kissing  bug,  76,  352. 
Kitasato,  279. 
Koch,  R.,  102,  327. 
Kreso  for  equine  mange,  334. 

for  lice,  68. 

for  hen  fleas,  293. 

for  sheep  dip,  295. 

for  sheep  scab,  343. 

Labrum-epipharynx,  25. 
Lachnosterna  arcuata,  48. 

fusca,  48. 
Lacinia,  25. 
Lantz,  D.  E.,  285. 
Larkspur,  for  head  louse,  66. 

for  lice,  68. 

for  pubic  louse,  67. 
Larvaecides,  126. 
Larvae,  insect,  13. 
Larvicide,  126. 
Latrine  fly,  242. 

larva  of,  263. 
Latrodectes  mactans,  12,  360. 
bite  of,  361. 
life  history  of,  363. 

mahnigniatus,  362. 
Laveran,  A.,  102. 
Lavender,  oil  of,  132. 
Laverania  malarise,  108. 
Lavinia  exilicauda,  133. 
Law,  James,  334. 
Lazear,  J.  W.,  113. 
LeConte,  J.  L.,  76. 


Leech,  medicinal,  10. 

Legislation  against  mosquitoes,  137. 

Leidy,  J.,  177. 

Leishman,  W.  B.,  328. 

Leishman  donovan  bodies,  73. 

Leishmania  donovani,  73. 

Lepidoptera,  22. 

larvae  of,  13. 

mouth  parts  of,  31. 
Leprosy,  Asturian,  145. 
Leptus  autumnalis,  345. 
Lesser  house  fly,  241. 

larva  of,  263. 
Leuciocus  crassicandra,  133. 
Lewis,  J.  R.,  210. 
Lice,  7,  36,  52. 

biting  (see  Biting  Uce). 

control  of,  57,  66,  68. 

dissemination  of,  65. 

sucking  {see  Sucking  Uce). 
Ligula,  27. 
Lime  sulphur  for  bovine  scabies,  343. 

chloride  of,  on  manure,  195. 

for  sheep  dip,  295. 

for  sheep  scab,  339. 

for  swine  mange,  332. 
Liotheidse,  53. 

species  of,  57. 
Lipeurus,  bacidus,  56. 

heterograijhus,  55. 

polytrapezius,  55. 

squalidus,  55. 

variabilis,  55. 
Lipoptena  depressa,  295. 
Liston,  W.  G.,  279. 
Lithobia,  374. 
Liverfluke,  of  cattle,  9. 

of  sheep,  9. 
Locusts,  19. 

Lone  star  tick,  301,  316,  321. 
Long,  J.  D.,  288. 
Lophoscelomjda,  97. 
Lord,  F.  T.,  180. 
Louse,  body,  60,  64. 

crab,  60. 

head,  59. 

pubic,  60. 
Louse  flies,  293. 

of  deer,  295. 

of  horse,  295. 

of  sheep   294. 
Low,  G.  C'.  (Sambon,  L.  W.,and),  102, 

105. 
LuciUa  caesar,  238. 
larvae  of,  263. 

serricata,  238. 
larvae  of,  263. 
Lumbricus  terrestris,  10. 
Lycosa  tarentula,  364. 
Lytta  vesicatoria,  49,  351. 

MacCullum,  W.  G.,  104. 
Mackie,  F.  P.,  63. 


INDEX 


387 


Macrogametes  of  malaria,  111. 
Maerogametocytes  of  malaria,  110. 
Maggots,  7,  13. 
Malaria,  101. 

sestivo-autumnal,  106. 

circumstantial    evidence    of    spread, 
102. 

control  organization,  134. 
cost  of,  134. 
educational  factor,  137. 
legislation,  137. 
ordinances,  139. 
results  of,  140. 

cycle  of  Golgi,  108. 

cycle  of  Ross,  108. 

economic  considerations,  2. 

experimental  evidence  of  spread,  103. 

gametes  of.  111. 

gametocytes  of,  110. 

historical  sketch  of,  101. 

inheritance  by  mosquitoes.  111. 

in  river  towns,  129. 

macrogametes  of.  111. 

maerogametocytes  of,  110. 

merocyte  of,  108. 

merozoite  of,  110. 

microgamete  of.  111. 

microgametocyte  of,  110. 

parasites  of,  105. 

parthenogenetic  cycle  of,  108,  110. 

quartan,  108. 

quotidian,  108. 

schizogonic  cycle  of,  108. 

sporogonie  cycle  of,  108. 

sporozoite  of,  108. 

tertian,  107. 

time  factor  in,  136. 

with  reference  to  temperature,  111. 
Malignant  pustule,  152. 
Mallophaga,  7,  21,  32,  52. 
Malmignatte,  362. 
Malpighian  tubules,  15. 
Mandibles,  25. 
Mandibulata,  24. 
Mange,  331. 

bovine,  334. 

canine,  335. 

equine,  333. 

foUicular,  344. 

of  camels,  335. 

of  cats,  335. 

of  goats,  335. 

of  swine,  332. 

treatment  of,  332,  334,  335. 
Manson,  Sir  Patrick,  102,  105,  111,  115, 

116,  240,  278. 
Manson,  P.  Thurburn,  102,  105. 
Manure  bins,  189. 

disposal,  187. 

insecticides  for,  193. 

ordinances,  199,  204. 
Marchoux,  E.,  326. 
Marchoux,  E.  (Simond,  P.  L.,  and),  115. 

2c 


Marett,  P.  J.,  119. 

Margaropus  annulatus,  3,  12,  34,  297, 
300,  307. 

control  of,  308. 

description  of,  300. 

economic  importance  of,  301. 

life  history  of,  301. 

relation  to  Texas  fever,  306. 
Marlatt,  C.  L.,  71. 
Mason,  C.  J.  (Esten,  W.  M.,  and),  42, 

175. 
Mastigoproctus  giganteus,  372. 
May  beetles,  47. 
May  flies,  21. 

mouth  parts  of,  32. 
Mayo,  N.  S.,  332. 
Maxillae,  25. 
McCoy,  G.  W.,  283. 
Mease,  James,  305. 
Mecoptera,  22,  32. 
Mediterranean  fruit  fly,  264. 
Megarhininse,  95,  99. 
Melanolestes  abdominalis,  77. 

picipes,  77. 
Meloidfe,  49,  351,  352. 
Melolontha  melolontha,  48. 

vulgaris,  48. 
Melophagus  ovinus  (see  Sheep  tick). 
Menopon  biseriatum,  8,  57. 

pallidum,  8,  57. 

titan,  8. 
Mentum,  25. 
Mercurial   ointment   for   pubic   louse, 

67. 
Mereurialis,  177. 
Merocyte  of  malaria,  108. 
Merozoite  of  malaria,  110. 
Messmates,  8. 
Metamorphosis,  18. 

complex  or  complete,  18. 

incomplete  or  simple,  18.  ' 

primitive,  18. 

simple  or  incomplete,  18. 
Microfilaria  banerofti,  115. 

development  of,  116. 
Microgamete  of  malaria,  111. 
Microgametocyte  of  malaria,  111. 
Midges,  81. 

columbacz,  149. 

Dixa,  82. 

owl,  118. 
MiUer,  259. 

MilUons,  Barbadoes,  133. 
MiUipedes,  11,  374. 

Minchin,  E.  A.  (Thompson,  D., and),  65. 
Minnows,  top,  133. 
MiteheU,  Evelyn,  100. 
MitcheU,  J.  D.,  231. 
Mites,  characteristics  of,  330. 

depluming,  336. 

floiir  and  meal,  349. 

folUcle,  344. 

harvest,  345. 


388 


INDEX 


Mites,  in  ears  of  rabbits,  etc.,  344. 
itch,  331. 

life  history  of,  331. 
louse-like,  348.  , 

mange,  331. 
poultry,  3,  12,  346. 
psoroptic,  337. 
sarcoptic,  330. 
scab,  337,  339. 
scaly  leg,  335. 
sheep  scab,  12,  339. 
web-spinning,  350. 
Mitzmain,  M.  B.,   153,  218,  221,  267, 

269. 
Moore,  Sir  W.,  177. 
Mosquito  control  organization,  134. 
cost  of,  134. 
educational  factor,  137. 
legislation,  137. 
ordinances,  139. 
results  of,  140. 
time  to  begin,  136. 
Mosquitoes,  80. 
Anopheline,  33,  88. 

adults,  88. 

dxu-ation  of  Life,  91. 

eggs,  88. 

flight,  92. 

hibernation,  92. 

larvae,  89. 

life  history,  90. 

pupae,  90. 
bites  of,  132. 
breeding  places,  120. 
characteristics,  80,  86. 
control  of,  120. 
f uraigants  for,  132. 
internal  anatomy  of,  84. 
life  history  of,  82. 
natural  enemies  of,  132. 
repellents,  131,  132. 
role  in  filariasis,  116. 
salt  marsh,  130. 
sexual  differences,  86. 
Yellow  fever,  92. 

adults,  92. 

eggs,  94. 

larvae,  95. 

life  history,  95. 

pupfe,  95. 
Mosquito  hawks,  132. 
Moths,  22. 

Mouth  parts,  classification,  24,  32. 
aphis  lions,  32. 
ant  lions,  32. 
ants,  32. 
bedbugs,  32. 
beetles,  32. 
book  lice,  32. 
bristletails,  32. 
butterflies,  32. 
cicadas,  32. 
cockroaches,  32. 


cone-noses,  32. 

damsel  flies,  32. 

dipteron  type,  28,  32. 

dobson  flies,  32. 

dragon  flies,  32. 

earwigs,  32. 

fleas,  32. 

general,  23,  28. 

grasshoppers,  32. 

hemipteron  type,  28,  32. 

honeybee,  31,  32. 

horsefly,  29,  32. 

house  fly,  31,  32. 

hymenopteron  type,  31,  32. 

lepidopteron  type,  31,  .32. 

May  flies,  32. 

mosquitoes,  28,  32. 

moths,  32. 

orthopteron  type,  24,  32. 

physopodan,  24,  27,  32. 

scorpion  flies,  32. 

siphonaptera,  32. 

springtails,  32. 

stable  fly,  30,  32. 

stone  flies,  32. 

termites,  32. 

thrips,  27,  32. 
Multiceps  multiceps,  256. 
Murray,  Andrew,  59. 
Mus  alexandrinus,  285. 

norvegicus,  285. 

rattus,  285.  _ 
Musca  domestica  (see  House  fly). 
Muscidae,  160. 

characteristics  of,  160. 
Muscidus,  99. 
Muscina  stabulans,  262. 
MutilUdae,  358. 
Mygale  hentzii,  364. 
Myiasis,  233. 

gastric,  243,  245. 

identification  of  larvae  in,  259. 

intestinal,  13,  243. 

treatment  of,  240. 
Myriapoda,  11,  373. 
Myzomyia,  112. 

minimus,  112. 
Myzorhinchella,  97. 
Myzorhynchus,  97,  112. 

sinensis,  112. 

Nagana,  152,  213. 

Naphthaline  flakes,  57. 

Nasonia  brevicornis,  198. 

Necator  americanus,  183. 

Necrophorus,  46. 

Needham,  J.  G.  (Comstock,  H.  J.,  and), 

17. 
Nemathelminthes,  8. 
NeoeeUia,  98. 
Neopsylla,  274. 
Nettling  hairs,  351. 
Neuroptera,  21,  32. 


INDEX 


389 


Neuropterous  larvae,  13. 

Newman,  S.  W.,  366. 

Newstead,  R.,  195. 

Nicofume,  126. 

NicoU,  Wm.,  182. 

Nicolle,  C.  N.,  64. 

Nicotine  for  mosquitoes,  125. 

for  sheep  dip,  341. 
'"No-see-ums, "  82. 
Nott,  J.  C,  113. 

NuttaU,  G.  H.  F.,  47,  60,  62,  72,  102, 
105,    113,    152,    177,    180,    212, 
279,  298,  326,  365. 
Nuttallia  equi,  320. 
Nj'ssorhynchus,  97,  112. 

fuliginosus,  112. 

Obligatory  parasites,  7. 
Odonata,  21,  32,  132. 
OEciacus,  70. 

herundinus,  70. 

vicarius,  70. 
(Estridse,  13,  246,  264. 
(Estrus  ovis,  255. 

larva  of,  265. 
Oiling  methods  for  mosquitoes,  122. 
OUve  fly  larva,  264. 
Ontological  evidence,  13. 
Ookinete,  111. 
Oothecum,  of  roach,  37. 
Ophthalmia,  182. 
Opsicoetes  personatus,  76,  352. 
Ordinances,  flv,  199. 

food,  205. 

manure,  199,  204. 

mosquito,  139. 

stable,  199,  201. 
Oriental  roach,  39. 
Ornithobius  bucephalus,  57. 
Ornithodorus  coriaceus,  298,  329,  365. 

damage  done,  329. 

megnini,  .328. 

moubata,  327,  370. 

savignyi,  329. 

treatment  for,  329. 
Oroya  fever,  117. 
Orthoptera,  19,  32. 

mouth  parts  of,  25. 
Osborn,  H.,  55,  236,  246,  255. 
Otaeariasis,  344. 
Otitis,  344. 

Otodectes  eygnotis,  344. 
Ovine  scabies,  338. 

symptoms,  338. 

treatment,  339. 
Ox  warble  (see  Warble  fly). 
Oxyuris  vermicularis,  183. 

Packard,  A.  S.,  165. 

Packard,  A.  S.  (Howard,  L.  O.,  and),  361. 

Pajaroello  tick,  329,  365. 

experiments  with,  366. 

life  history  of,  369. 


Palpus,  25. 
Pangonia,  156. 
Panophtes,  99. 
Papatici  fever,  119. 

flies,  82. 
Paraplasma  flavigenum,  114 
Parasimulium,  147. 
Parasita,  58,  69. 
Parasitism,  6. 

degrees  of,  8. 

external,  36. 

internal,  36. 
Paris  green,  195.     - 
Parthenogenetic  cycle  of  malaria,  110. 
Pasture  rotation,  311. 
Pathogenic  organisms,  environment  of, 

33. 
Patten,  W.  S.,  73. 
Peach  twig  borer,  348. 
PedicuUdse,  58. 
Pediculoides,  330. 

ventricosus,  348. 
Pediculosis,  58,  62. 
Pediculus  capitis,  59. 

vestimenti,  60,  64. 
Pedipalpida,  372. 
Pelican,  8. 
Pellagra,  145. 

Pelopoeus  cementarius,  359. 
Pemphigus  contagiosus,  62. 
Pennyroyal,  oil  of,  132. 
Peripatus,  11. 
Periplaneta  americana,  39. 

australasia,  39. 
Pfeiffer,  R.,  102. 
Phenol,  for  head  louse,  67. 
Philopteridse,  53. 

species  of,  55. 
Phlebotomus,  82,  118. 
Phlebotomus  papatasii,  119. 

verrucarum,  118. 
Phleothrips  nigra,  51. 

verbasci,  51. 
Phorbia  brassieae,  243. 
Phormia  regina,  238. 
Phthiriasis,  58,  62. 
Phthirius  inguinalis,  61. 
Physopoda,  22,  32,  50. 

mouth  parts  of,  27. 
Pike,  Sacramento,  133. 
Piper,  S.  E.,  289. 
Piroplasmia  bigemina,  305,  306. 

hominis,  314. 
Piroplasmosis,  305. 
Plague,  33,  278. 

transmission  of,  278. 

by  squirrels,  283. 

Plasmodium,  33,  35,  105. 

detection  of,  105. 

falciparum,  106. 

falciparum  quotidianum,  108. 

life  history  of,  108. 

malariae,  108. 


390 


INDEX 


Plasmodium  praecox,  108,  110. 

vivax,  8,  107,  110. 
Plaster  of  pans,  against  roaches,  44. 
Platyhelminthes,  8. 
Plecoptera,  21,  32. 
Plotz,  Harry,  65. 
Pogonomyrmex,  358. 
Poliomyelitis,  221. 
Polistes  pallipes,  359. 
Polybia  flavitarsis,  359. 
Pontia  rapse,  mouth  parts,  31. 
Porchiaski,  I.,  155. 
Potassium  dichroraate,  195. 
Poultry  Uce,  control  of,  57. 

mite  {see  Dermanyssus  gallinse). 
Predaeeous,  6. 
Privy,  sanitary,  192. 
Prosimulium,  147. 
Proteosoma,  104. 
Protozoa,  classification  of,  377. 
Protraeheata,  11. 
Proust,  A.,  47. 
Proventriculus,  14. 
Pruritis,  62. 
Psoeidse,  8. 
Psorophora,  99. 
Psoroptes  communis  var.  bovis,  343. 

var.  equi,  344. 

var.  ovis,  12,  330,  337,  338. 
Psoroptic  acariasis,  330. 
Psychodidae,  82,  118. 
Ptinus,  47. 

Ptychocheilus  grandis,  133. 
Pulex,  274. 

irritans  (see  Fleas),  8,  270,  275. 
PuUcidae,  273. 
Punkies,  82. 

Pyrethrum  powder,  57,  197. 
Pyxetophorus,  97. 
Pyrofume,  132. 
PyroUgneous  acid,  195. 
Pyrosoma  bigemina,  306. 

Quotidian  malaria,  108. 

Rabbit  bot,  257. 
Ransom,  B.  H.,  3. 
Rasahus  biguttatus,  77,  353. 

var.  thoraeieus,  78. 
Rat  control,  285. 
Rat,  fllaria  of,  43. 

fleas  of,  2,  270,  276,  277. 
Rat-tailed  larva,  244. 
Red  bugs,  345. 
Red-tailed  bot,  250. 
Reduviidse,  75,  352. 
Reduvius  personatus,  76,  352. 
Reed,  Walter,  95,  113. 
Relapsing  fever,  63,  73. 
Repellents,  mosquito,  131. 
Repp,  John  J.,  347. 
Rhicephalus,  323. 

appendiculatus,  314. 


bursa,  320. 

capensis,  314. 

eyersti,  314,  320. 

nitens,  314. 

sanguineus,  320,  321. 

simus,  314. 
Rhipicentor,  322. 
Richardson,  M.  W.,  222. 
Ricketts,  H.  T.,  64,  315. 
Ricketts,  H.  T.  (Wilder,  R.  N.,  and),  64. 
Roach  (a  fish),  133. 

American,  39. 

AustraUan,  39. 

control,  44. 

disease  transmission  by,  40. 

Oriental,  39. 

Pennsylvanian,  39. 

poison,  44. 
Robertson,  W.,  313. 
Root  maggot  fly,  242. 
Rosenau,  M.  J.,  223. 
Ross,  R.,  102,  105,  108,  110. 

cycle  of,  108. 
Roundworms  of  man,  8. 
Rove  beetles,  45. 
Rucker,  W.  C,  286. 

Sabethes,  100. 
Salivary  reservoirs,  15. 

system  of  insects,  15. 
Salmon,  D.  E.,  305,  307. 
Salt  marsh  mosquitoes,  130. 
Sambon,  L.  W.,  145,  146. 
Sambon,  L.  W.  (Low,  G.  C,  and),  102, 

105. 
Sand  flea,  274,  291. 
Sarcophaga  sarraceniae,  238. 
Sarcophagidse  {see  Flesh  flies). 
Sarcopsylla,  274. 

penetrans,  278,  291. 
SarcopsylUdae,  273,  274. 
Sarcoptes  minor  var.  felis,  335, 

mutans,  335. 
Sarcoptes  scabiei,  331. 

var.  cameU,  335. 

var.  canis,  335. 

var.  caprse,  335. 

var.  equi,  331,  333. 

var.  hominis,  331,  332. 

var.  suis,  330,  331,  332. 
Sarcoptic  acariasis,  330. 
Sarcoptidae,  330,  337. 
Saw-toothed  grain  beetle,  48. 
Sawyer,  W.  A.,  224,  366. 
Scabies,  337. 

bovine,  343. 

equine,  344. 

ovine,  338. 

treatment,  343,  344. 
Scaly  leg  of  fowls,  335. 

treatment,  336. 
Scarabaeidae,  47. 
Scavenger  beetles,  45. 


INDEX 


391 


Scavenger  flies  {see  Flesh  flies). 
Schizogonic  cycle  of  malaria,  108. 
Schizotrypanum  cruzi,  79. 
Schmidt,  C.  L.  A.,  203. 
Sehiiffner's  dots,  107. 
Sclerostomum  equinum,  183. 
Seolopendra  heros,  374. 
Scorpionida,  370. 
Scorpion  flies,  22,  32. 
Scorpionidae,  371. 
Scorpions,  12,  370. 

classification,  371. 

characteristics,  370. 

sting  of,  371. 

whip,  372. 

wind,  373. 
Screening  for  mosquitoes,  131. 
Screw  worm  fly,  3,  6,  234. 

as  affecting  animals,  237. 

as  affecting  man,  235. 

hfe  history  of,  234. 
Scurvy,  Alpine,  145. 
Seal,  W.  P.,  133. 
SeideUn,  H.,  114. 
Septicsemic  infection,  35. 
Shamberg,  J.  F.   (Goldberger,  J.,  and), 

349. 
Sheep  louse  fly,  294. 

maggot  fly,  238. 
Sheep  scab  {see  Ovine  scabies). 

tick,  294. 

life  history  of,  294. 
pathogenesis,  294. 
Shiner,  133. 

Signet  ring  in  malaria,  108. 
Silpha,  46. 
Silphidaj,  46. 
Silvius,  156. 
Simmonds,  M.,  181. 
Simond,  P.  L.,  279. 

Simond,  P.  L.  (Marchoux,E.,and),  115. 
Simpson,  F.,  287. 
Simuliidse  {see  Buffalo  gnats). 
Simuhum  columbaczense,  149. 

meridionale,  148. 

oecidentale,  148. 

pecuarum,  147. 

venustum,  148. 
Siphonaptera  (see  Fleas),  22,  32,  353. 
Sitotroga  cerealella,  348. 
Sleeping  sickness,  African,  8, 34, 35,  210. 

control  of,  213. 

reservoirs,  212. 

transmission  of,  212. 
Smith,  J.  B.,  71,  89,  132. 

Theobald,  305,  306. 
Snodgrass,  R.  E.,  355. 
Sodium  cyanide  for  fly  larvae,  195. 
SoUman,  T.,  50. 
Solpugidse,  373. 
Sowbug,  10,  11. 
Spanish  fly,  49. 
Sphserophthalmia  occidentaUs,  358. 


Sphecina,  359. 
Sphecius  speciosus,  359. 
Spiders,  359. 

bird,  364. 

black  widow,  360. 

hour  glass,  360. 

red,  350. 

sun,  373. 

trap-door,  364. 
Spillman  and  Haushalter,  180. 
Spinose  ear  tick,  328. 
Spirillum  cholerae,  181. 
Spirochaeta  carteri,  63. 

duttoni,  63,  73,  327. 

gallinarum,  325. 

marchouxi,  325. 

novyi,  63. 

pertenuis,  181. 

recurrentis,  63,  73. 
Spiroehsetosis,  62,  63,  73. 

fowl,  325. 
Sporogonic  cycle  of  malaria,  108. 
Sporozoa,  9. 

Sporozoite  of  malaria,  108,  111. 
Spotted  fever,  314. 

symptoms  of,  314. 

tick  transmission  of,  315. 
Sprays  as  repellents,  231. 
Spring  tails,  32. 
Squirrel  flea,  269,  276,  283. 
Squirrels   as   disseminators   of  plague, 
283 

control,  287. 

ground,  283. 

poison,  289. 
Stable  construction,  185. 

ordinance,  201. 
Stable  fly,  215. 

as  a  cattle  pest,  221. 

breeding  habits,  216. 

characteristics,  215. 

control  of,  228. 

habits,  216. 

in  relation  to  infantile  paralysis,  221. 
poHomyehtis,  221. 
smra,  221. 

larva  of,  262. 

Ught  reactions  of,  216. 

longevity  of,  219. 

mouth  parts  of,  24,  30,  32. 
Staggers,  255. 
Staphyhnidse,  45. 
Staphylinus,  46. 
Staphylococcus  aureus,  174. 
Stegomyia,  5,  35,  87,  92. 

calopus,  88,  114. 
Stephens,  J.  W.   W.    (Christophers,  S. 
R.,  and),  87,  88,  95, 107, 110, 208, 
213. 
Sternberg,'G.  M.,  113. 
Stethomyia,  97. 
Stick  tight  flea,  292. 
Stiles,  C.  W.,  183,  192,  259. 


392 


INDEX 


# 


Sting  {see  Honeybee  sting). 

of  scorpion,  371. 
Stinging  insects,  357. 
Stipes,  25. 
Stomoxys  calci trans  (see  Stable  flv). 

glauca,  228. 

inornata,  228. 

nigra,  228. 
Stone  flies,  31,  32. 
Submentum,  25. 
Sucking  lice,  58. 

in  relation  to  disease,  62. 

life  history  of,  58. 

of  dog,  61. 

of  field  mouse,  62. 

of  ground  squirrel,  62. 

of  hog,  61. 

of  horse,  61. 

of  ox,  61. 

of  rat,  62. 

of  sheep,  61. 

of  white  footed  mouse,  62. 
Sulphur,  for  body  louse,  67.    ^"^ 

for  roaches,  44. 

fumigation,  75. 
Summer  diarrhea,  179. 
Sun  disease,  145. 
Sun  spider,  373. 
Surra,  152. 
Swingle,  L.  D.,  294. 
Sydenham,  T.,  177. 
Sylvanus  surinamensis,  48. 
Symbiotes  auricularum,  344. 
Syphilis,  63. 
Syrphids,  244. 

TabanidjB,  7,  34,  149,  155. 
Tabanus  atratus,  156. 

costaUs,  157. 

dorsovittata,  212. 

lineola,  158. 

mouth  parts  of,  29. 

punctifer,  157. 

striatus,  153,  158. 

stygius,  157. 
wing  of,  16. 
Taenia  cueumerina,  65. 

expansa,  19. 

serrata,  183. 

soUum,  9,  183. 

marginata,  183. 
TiBniorhynchus,  99. 
Tapeworm  of  cattle,  9. 

of  dog,  9,  65. 

of  man,  9. 

of  poultry,  9. 
Tarantulas,  360,  364. 
Tarantism,  364. 
Tarbardillo,  64. 
Tarsonemidse,  348. 
Termites,  21. 
Tetranj^chidae,  350. 
Texas  fever,  3,  34,  305. 


Texas  fly  {see  Horn  fly). 

screw  worm  {see  Screw  worm  fly). 
Theileria  parva,  313. 
Thelyphonidae,  372. 
Theobald,  F.  V.,  94,  95. 
Theobaldia  incidens,  88. 
Thompson,   D.  (Minchin,  E.  A.,  and), 

65. 
Thornheaded  worm,  47. 
Thousand-legged  worm,  373. 
Thrips,  22,  27,  50. 

clover,  51. 

grass,  51.  , 

mullein,  51. 

pear,  51. 
Thysanoptera,  22,  27,  50. 
Thysanura,  16,  18,  32. 
Ticks,  296. 

adobe,  323. 

argasine,  323. 

bite  remedies,  370. 

"castor  bean,"  321. 

classification  of,  298,  321. 

deer,  321. 

dog,  303,  321. 

feeding  habits  of,  297. 

fowl  {see  Argas  persicus). 

Ixodine,  300,  321. 

life  history  of,  297. 

•'lone  star,"  321. 

longevity  of,  298.  , 

mouth  parts  of,  297. 

PajaroeUo,  329,  365. 

paralysis  caused  by,  320. 

rabbit,  321. 

relapsing  fever,  326. 

sheep,  294. 

spinose      ear      (see     Ornithodoius 
megnini). 

spotted  fever,  317. 
control  of,  319. 
description  of,  317. 
distribution  of,  318. 
life  history  of,  317. 
longevity  of,  318. 

tampan,  323. 

Texas  fever,  3,  12.  3(X). 

venomous,  364. 

wood,  303,  321. 
Tipulidffi,  80,  81. 
Tizzoni,  G.,  181. 
"Tlalsahuate,"  345. 
Tobacco  decoction  for  lice,  68. 

for  mosquitoes,  125. 

dip  for  sheep  scab,  341. 

dust  bath,  57. 
Todd,  J.  L..  327. 
Torti,  102. 

Townsend,  C.  H.  T.,  118,  119 
Toxascaris  Umbata,  183. 
Toxorhynchites,  99. 
Tracheal  breatliing  system,  13. 
Transitory  parasites,  7. 


/ 


INDEX 


393 


Trematoda,  7,  9. 
Treponema  pallidum,  63. 
Triatoma  megistus,  79. 
Trichinella  spiralis,  8. 
Trichinosis,  8. 

Trichocephalus  triehiurus,  183. 
Trichodectes  climax,  54. 
hermsi,  54. 
latus,  54,  65. 
parumpilosus.  54. 
scalaris,  54. 
subrostratus,  54. 
tibialis,  55. 
Trichodectidae.  53. 

species  of,  54. 
Trichoprosopon,  99. 
Trichoptera,  22.  32. 
Triehuris  triehiurus,  183. 
Trinoton  hturatum,  57. 

luridum,  57. 
Troctes  divinatoria.  S. 
Trombidiidse,  345. 

life  history  of,  345. 
Trombidium  holosericeum.  345. 

magnificum,  345. 
Trypanosoma  brucei,  213. 
castellani,  210. 
evansi,  152,  221. 
gambiense,  8,  9,  34,  210. 
lewisi,  209. 
rhodesiense,  211. 
ugandense,  210. 
Trypanosomiasis.  208. 
BraziUan,  79. 
rat,  65. 
Trypetidae,  264. 
Tsetse  flies,  207. 

characteristics  of,  207. 
classification  of,  214. 
habits  of,  207. 
life  history  of,  208. 
relation  to  disease,  208. 
Tuberculosis,  33,  177. 
Tumbu  flv,  238. 
Turkey  gnat,  148. 
Turpentine  for  bots,  249. 
Two-spotted  corsair,  77,  353. 
Tyroglyphus  farinse,  349. 

siro,  349. 
Typhlopsylla,  274. 
Typhoid  fever.  177. 
Typhus  fever,  36,  64. 
Tvroglvphidae,  349. 
Tyzzer,  E.  E.,  352. 

Ulcer,  tropical,  181. 
Uranotaenia,  100. 
Uropodidse,  346. 

Van  Duzee,  E.  P.,  77. 
Vejovidae,  371. 


Vejovis  carolinus,  371. 

Velvet  ants,  358. 

Venomous  insects  and  arachnids,  351. 

Venoms,  hasmolytic,  351. 

haemorrhagie,  351. 

how  introduced,  351. 

insect,  36,  351. 

neurotoxic,  351. 

scorpion,  351. 

spider,  360. 

tick,  364. 
Verjbitsky,  A.  T.,  279. 
Verrucca  peruana,  117. 
Verruga,  117. 

mode  of  transmission,  118. 
Vespa  maculata,  359. 
Vinegerone,  372. 

Warble  fly  {see  Warbles). 
Warbles,  ox,  3,  13,  251. 

characteristics  of,  251. 

economic  losses  due  to,  253. 

in  humans,  258,  264. 

injury  done  by,  252. 

life  history  of,  251. 

prevention  of,  254. 

treatment  for,  254. 
Warburton,  C,  60. 
War  fever,  64. 
Warren,  George,  102,  105. 
Washburn,  F.  L.,  249. 
Webster,  F.  M.,  349. 
Wellman,  F.  C,  328,  370. 
Whip  scorpions,  372. 
White  ants,  mouth  parts  of,  32. 
Wilder,  R.  N.  (Ricketts,  H.  T.,  and), 

64. 
WiUiston,  S.  W.,  81,  160,  246,  293. 
Wilson,  L.  B.,  315. 
Wind  scorpions,  373. 
Wing  of  tabanus,  16. 
Wings  of  insects,  15. 
Wool  sorter's  disease,  152. 
Wyeomjda,  100. 

Xenopsylla,  274. 

cheopis,  270,  277,  279. 
Xestopsylla  gallinacea,  292. 

Yaws,  181. 

Yellow  fever,  3,  5,  113. 

commission,  113. 

etiology  of,  114. 

mosqvuto  carrier,  113. 
Yersin,  279. 

Zenoleum  for  depluming  mites,  336. 
for  hen  flea,  293. 
for  sheep  scab,  343. 
for  sheep  tick,  295. 


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7 


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and  on  a  scientific  basis.  There  has,  up  to  the  present,  been 
no  book  in  English  presenting  in  detail  the  physiology  of  diges- 
tion and  metabolism  in  infancy  — •  which  must  form  the  basis  of 
all  scientific  and  rational  infant  feeding — -and  none  describing 
in  detail  how  to  feed  babies  according  to  the  indications  in 
the  individual  case.  The  authors  first  present  the  scientific 
facts  on  which  each  condition  is  based,  and  then  apply  them 
practically  and  in  detail. 


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NEW  MEDICAL   BOOKS 


Diseases  of  the  Arteries 
Including  Angina  Pectoris 


By 


THOMAS  CLIFFORD  ALLBUTT,  M.A.,  M.D.,  LL.D.,  F.R.C.P.,  F.R.S. 

Regius  Professor  of  Physic  in  the  University  of  Cambridge,  etc. 
Editor-in-Chief  of  "  A  System  of  Medicine  " 

Illustrated,  Cloth,  2  vols.,  8vo,  $g.oo 
To  this  work  Doctor  Allbutt  has  brought  the  conclu- 
sions of  a  ripe  experience  combined  with  a  rare  Hterary  gift 
of  expression.  While  covering  some  of  the  paths  of  com- 
mon knowledge  he  has  written  at  greatest  length  on  con- 
ditions which  he  has  personally  experienced  and  which  are 
most  unusual.  The  work  is  comprehensive  in  detail  and 
is  invaluable  to  every  practitioner  who  is  in  any  way  in- 
terested in  this  group  of  diseases,  which  is  at  present  re- 
ceiving so  much  attention  from  the  medical  profession. 

The  Criminal  Imbecile 

By  henry   H.   GODDARD 

Director  of  the  Training  School  for  Feebleminded  Children  at  Vineland,  N.J.,  and  Author  of 
"  The  Kallikak  Family,"  "  Feeblemindedness  :  Its  Causes  and  Consequences,"  etc. 

Illustrated,  Cloth,  i2mo,  $1.50 

This  is  an  analysis  of  three  murder  cases,  in  which  the 
Binet  tests  were  used,  accepted  in  court  and  the  accused 
adjudged  imbeciles  in  the  legal  sense  (scientifically,  morons). 
Three  types  of  defectives  are  illustrated  in  the  three  cases. 
Responsibility  is  discussed.  The  book  is  important  to  all 
practitioners  in  psychiatry,  students  of  feeble-mindedness 
and  social  problems,  and  to  criminal  lawyers. 


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Children's  Diseases  for  Nurses 


By  HERMAN   SCHWARZ,  M.D. 

Lecturer  in  Children's  Diseases,  Mt.  Sinai  Hospital  Training  School,  New  York;  Instructor  in 
Children's  Diseases  at  the  Post  Graduate  Medical  School,  New  York,  etc. 


A.   S.   BLUMGARTEN,   M.D. 

Lecturer  in  the  Training  School  of  the  German  Hospital,  New  York ;  author  of  "  Materia  Medica 

for  Nurses,"  etc. 

(Preparing) 

A  long-felt  need  for  an  up-to-date  text  on  the  nursing 
of  children's  diseases  has  led  these  well-known  authors  to 
prepare  this  work  especially  for  the  use  of  pupil  nurses  in 
training  schools.  It  is  written  in  a  thorough,  practical,  easy 
and  simple  style.  It  combines  Doctor  Schwarz's  broad 
knowledge  of  children's  diseases  with  Doctor  Blumgarten's 
experience  as  a  successful  teacher  and  writer  on  nursing 
subjects,  whose  text-book  on  Materia  Medica  in  the  first 
year  of  its  publication  is  already  used  by  hundreds  of  Train- 
ing Schools.  This  new  text  is  an  invaluable  aid  to  teachers 
and  nurses  in  hospitals  and  is  the  first  comprehensive  and 
essentially  practical  work  so   far  published  on    the  subject. 


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Publishers  64-66  Fifth  Avenue  New  York 


